Org assignment history, mobile support, and a correctness pass

Data model
- employee_assignments records org placement over time (valid_from/valid_to),
  written by a trigger on `employees` rather than inside each RPC: ~70
  `update employees` statements spread over fifteen migrations mean per-call
  bookkeeping would miss paths today and again with every future RPC. A
  partial unique index enforces the one-open-interval invariant the trigger
  relies on when closing the current row.
- The Organigramm gains a Stichtag (default today). Membership comes from
  entry/exit/karenz, past placement from the new history, future placement
  projected from pending_org_changes. Placements predating the migration are
  backfilled with today's values and flagged as such in the UI, since
  employee_history only ever stored free text and cannot be reconstructed.

Correctness
- Reports and exports silently truncated at PostgREST's 1000-row cap
  (db.max_rows); employee_history is already past it at ~800 staff. Every
  whole-table read now pages explicitly.
- XLSX date cells were a day early: ExcelJS converts a Date to an Excel
  serial straight off getTime(), so a Date built at local midnight lands on
  the previous day's serial in any positive-offset zone.
- Date handling is pinned to Europe/Vienna throughout, and date-only strings
  are formatted without a Date round-trip. The dashboard's YTD window was
  built by round-tripping a local Date through toISOString(), which shifted
  it a day early and dropped 31 December entirely.
- Export routes parsed measure/group/split/eventType with unchecked `as`
  casts, so an unknown value reached column headers as `undefined` and the
  Content-Disposition filename. Parsed against the label maps now, with the
  filename slugged as a backstop.
- toXlsx keyed columns by header text, silently dropping the second of any
  two columns sharing a name — split columns take their header from data.
- The org chart tree walks had no cycle guard; nothing in the schema forbids
  a manager_id cycle, and one would hang the tab rather than misreport.
- The login page reflected ?error= verbatim, letting anyone put arbitrary
  text on the real sign-in screen; messages are looked up by code now.
- React Flow needs elementsSelectable on, or it sets pointer-events:none on
  the whole node and the expand control stops responding.

UI
- Mobile: the shell was unusable below lg — a fixed 236px margin pushed
  content off-screen with no mobile navigation at all. The sidebar is now a
  drawer, dvh replaces vh, safe-area insets are honoured, inputs are 16px so
  iOS stops zooming on focus, and form grids stack.
- Org chart nodes redesigned: per-kind accent stripes and icons, vacant
  roles called out, expand control moved to the bottom edge carrying the
  child count.
- Pagination is windowed; it previously rendered one link per page (54 for
  the employee list, unbounded for the audit log).
- Positions page reduced to open positions with a single "Besetzen" action.
- The employee Organisation tab links into the org chart focused on that
  person, reusing the chart's existing search-match highlighting.

Also included, uncommitted until now
- Dependants, HR notes, academic titles, split address fields, position
  validity and role/employment fields, with their migrations and UI.
- Docker/compose deployment setup, data-model and security-review docs.

supabase/migrations/20260716120000_position_validity_and_delete.sql

@@ -0,0 +1,183 @@
+-- Position validity window + delete capability.
+--
+--   1. Positions had no "gültig ab" (valid_from) date — nothing recorded
+--      since when a position is actually meant to be active, so a position
+--      created today for a future need could immediately be staffed/hired
+--      into.
+--   2. There was no way to remove a position again once created (no UI, no
+--      Server Action, no RPC) — a mis-created or no-longer-needed open
+--      requisition was stuck forever.
+--   3. Neither staff_position_internally nor hire_employee checked the
+--      position's validity window before assigning an employee to it.
+
+alter table positions add column if not exists valid_from date not null default current_date;
+
+-- ── Position ausschreiben: now records valid_from ────────────────
+create or replace function create_position(payload jsonb)
+returns uuid language plpgsql as $$
+declare
+  v_id uuid;
+  v_superior_id uuid := (payload->>'superior_employee_id')::uuid;
+  v_is_lead boolean := coalesce((payload->>'is_lead')::boolean, false);
+  v_team_id uuid;
+  v_valid_from date := coalesce(nullif(payload->>'valid_from', '')::date, current_date);
+begin
+  perform require_hr_admin();
+
+  if v_is_lead then
+    v_team_id := (payload->>'team_id')::uuid;
+  else
+    select team_id into v_team_id from employees where id = v_superior_id;
+  end if;
+
+  insert into positions (title, team_id, is_lead, reports_to_employee_id, valid_from)
+    values (payload->>'title', v_team_id, v_is_lead, v_superior_id, v_valid_from)
+    returning id into v_id;
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, details)
+    values (auth.uid(), current_actor_name(), 'Ausschreibung', payload->>'title', 'Position ausgeschrieben, gültig ab ' || v_valid_from);
+
+  return v_id;
+end;
+$$;
+
+-- ── Position löschen ───────────────────────────────────────────────
+-- Only open (unfilled) positions can be deleted — a filled position is
+-- already tied to an employee's history/audit trail and to whoever holds it.
+create or replace function delete_position(payload jsonb)
+returns void language plpgsql as $$
+declare
+  v_position record;
+begin
+  perform require_hr_admin();
+
+  select * into v_position from positions where id = (payload->>'position_id')::uuid;
+  if not found then
+    raise exception 'Position nicht gefunden.';
+  end if;
+  if v_position.status <> 'open' then
+    raise exception 'Nur offene Positionen können gelöscht werden.';
+  end if;
+
+  delete from positions where id = v_position.id;
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, details)
+    values (auth.uid(), current_actor_name(), 'Position gelöscht', v_position.title, 'Position ' || v_position.position_number || ' gelöscht');
+end;
+$$;
+
+-- ── Intern besetzen: reject if the position isn't valid yet ─────────
+create or replace function staff_position_internally(payload jsonb)
+returns void language plpgsql as $$
+declare
+  v_position record;
+  v_employee_id uuid := (payload->>'employee_id')::uuid;
+  v_manager uuid;
+  v_name text;
+begin
+  perform require_hr_admin();
+  select * into v_position from positions where id = (payload->>'position_id')::uuid and status = 'open';
+  if not found then
+    raise exception 'Position ist nicht mehr offen.';
+  end if;
+  if v_position.valid_from > current_date then
+    raise exception 'Die Position ist erst ab % gültig.', to_char(v_position.valid_from, 'DD.MM.YYYY');
+  end if;
+  select first_name || ' ' || last_name into v_name from employees where id = v_employee_id;
+
+  v_manager := resolve_manager_for(v_position.team_id, v_position.is_lead, v_position.division_id);
+
+  update employees set
+    team_id = v_position.team_id,
+    job_title = v_position.title,
+    source = 'Intern',
+    is_lead = case when v_position.is_lead then true else is_lead end,
+    org_level = case when v_position.is_lead then 2 else org_level end,
+    manager_id = v_manager
+  where id = v_employee_id;
+
+  if v_position.is_lead then
+    update employees set manager_id = v_employee_id
+      where team_id = v_position.team_id and id <> v_employee_id and is_lead = false and status <> 'Ausgetreten';
+  end if;
+
+  update positions set status = 'filled', filled_at = now(), filled_by_employee_id = v_employee_id
+    where id = v_position.id;
+
+  insert into employee_history (employee_id, event_date, event_type, description)
+    values (v_employee_id, current_date, 'Versetzung', 'Interne Besetzung: ' || v_position.title);
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, target_employee_id, details)
+    values (auth.uid(), current_actor_name(), 'Interne Besetzung', v_name, v_employee_id, v_position.title);
+end;
+$$;
+
+-- ── Neueinstellung: reject if entry_date precedes the position's validity ──
+create or replace function hire_employee(payload jsonb)
+returns uuid language plpgsql as $$
+declare
+  v_id uuid;
+  v_team_id uuid;
+  v_division_id uuid;
+  v_position record;
+  v_job_title text;
+  v_email text;
+  v_manager uuid;
+begin
+  perform require_hr_admin();
+
+  if payload->>'position_id' is not null then
+    select * into v_position from positions where id = (payload->>'position_id')::uuid and status = 'open';
+    if not found then
+      raise exception 'Position ist nicht mehr offen.';
+    end if;
+    if (payload->>'entry_date')::date < v_position.valid_from then
+      raise exception 'Das Eintrittsdatum darf nicht vor dem Gültigkeitsbeginn der Position (%) liegen.', to_char(v_position.valid_from, 'DD.MM.YYYY');
+    end if;
+    v_team_id := v_position.team_id;
+    v_division_id := v_position.division_id;
+    v_job_title := coalesce(payload->>'job_title', v_position.title);
+  else
+    v_team_id := (payload->>'team_id')::uuid;
+    select division_id into v_division_id from teams t join departments d on d.id = t.department_id where t.id = v_team_id;
+    v_job_title := payload->>'job_title';
+  end if;
+
+  v_manager := resolve_manager_for(v_team_id, false, v_division_id);
+  v_email := generate_company_email(payload->>'first_name', payload->>'last_name');
+
+  insert into employees (
+    first_name, last_name, gender, birth_date, sv_nummer, nationality, email, phone,
+    team_id, division_id, job_title, location_id, manager_id, org_level, is_lead,
+    employment_type, weekly_hours, contract_type, contract_end_date,
+    paygrade, source, status, entry_date
+  ) values (
+    payload->>'first_name', payload->>'last_name', (payload->>'gender')::gender_type,
+    (payload->>'birth_date')::date, payload->>'sv_nummer', coalesce(payload->>'nationality', 'Österreich'),
+    v_email, payload->>'phone',
+    v_team_id, v_division_id, v_job_title, (payload->>'location_id')::uuid,
+    v_manager, 3, false,
+    coalesce((payload->>'employment_type')::employment_type, 'Vollzeit'),
+    coalesce((payload->>'weekly_hours')::numeric, 38.5),
+    coalesce((payload->>'contract_type')::contract_type, 'unbefristet'),
+    nullif(payload->>'contract_end_date', '')::date,
+    coalesce((payload->>'paygrade')::paygrade_type, 'B'),
+    coalesce((payload->>'source')::source_type, 'Extern'),
+    (case when (payload->>'entry_date')::date > current_date then 'Geplant' else 'Aktiv' end)::employment_status,
+    (payload->>'entry_date')::date
+  ) returning id into v_id;
+
+  if payload->>'position_id' is not null then
+    update positions set status = 'filled', filled_at = now(), filled_by_employee_id = v_id
+      where id = (payload->>'position_id')::uuid;
+  end if;
+
+  insert into employee_history (employee_id, event_date, event_type, description)
+    values (v_id, (payload->>'entry_date')::date, 'Eintritt', 'Eintritt als ' || v_job_title);
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, target_employee_id, details)
+    values (auth.uid(), current_actor_name(), 'Neueinstellung', (payload->>'first_name') || ' ' || (payload->>'last_name'), v_id, 'Eintritt am ' || (payload->>'entry_date'));
+
+  return v_id;
+end;
+$$;