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/20260719120000_employee_notes.sql

@@ -0,0 +1,107 @@
+-- HR-Notizen: add-only Notizen zu einem Mitarbeiter, mit optionalem
+-- "Wiedervorlage am"-Datum. Kein Bearbeiten/Löschen — ein Fehler wird nicht
+-- korrigiert, sondern bleibt sichtbar (ggf. per neuer Notiz richtiggestellt),
+-- gleicher Append-only-Geist wie employee_history/audit_log.
+--
+-- Bewusst NICHT nach Autor gescoped und NICHT effective-dated: anders als
+-- employee_dependents sieht jede aktive HR-Person jede offene Notiz,
+-- unabhängig davon wer sie geschrieben hat oder zu wem sie gehört ("Meine
+-- Notizen" ist trotz des Namens ein geteiltes Team-Postfach), und eine
+-- Notiz hat keinen "existiert erst ab einem künftigen Datum"-Zustand wie
+-- eine Versetzung/Beförderung.
+--
+-- Kein Eintrag in employee_history: history_event_type ist ein fixer Enum
+-- (siehe 20260601000000_initial_schema.sql) ohne passenden Wert, und
+-- Historie ist explizit eine Beschäftigungsereignis-Timeline. Jede Mutation
+-- schreibt stattdessen nur einen audit_log-Eintrag.
+create table employee_notes (
+  id uuid primary key default gen_random_uuid(),
+  employee_id uuid not null references employees(id) on delete cascade,
+  author_user_id uuid references auth.users(id),
+  author_name text not null,
+  category text not null default 'Allgemein' check (category in (
+    'Allgemein', 'Vertraulich', 'Personalgespräch', 'Wiedervorlage', 'Lob / Anerkennung'
+  )),
+  note_text text not null,
+  due_date date,
+  done boolean not null default false,
+  done_at timestamptz,
+  done_by uuid references auth.users(id),
+  created_at timestamptz not null default now()
+);
+create index on employee_notes (employee_id);
+-- Deckt die "Meine Notizen"-Postfach-Query (loadOpenNotes) ab, die immer
+-- auf done = false filtert.
+create index on employee_notes (created_at desc) where not done;
+
+-- RLS narrows only what an already-GRANTed role may do; die
+-- "grant all ... to anon, authenticated, service_role"-Default-Privilegien
+-- (20260714120500_default_grants.sql) decken die neue Tabelle bereits ab.
+alter table employee_notes enable row level security;
+-- Eine einzige Blanket-Policy, gleiches Muster wie `positions`: offen vs.
+-- erledigt ist ein reiner App-Filter, nie eine RLS-Unterscheidung — jede
+-- aktive HR-Person darf jede Notiz lesen/schreiben.
+create policy "employee_notes_hr_all" on employee_notes for all
+  using (is_hr_user()) with check (is_hr_user());
+
+-- ── HR-Notiz hinzufügen ───────────────────────────────────────────────
+create or replace function add_employee_note(payload jsonb)
+returns uuid language plpgsql as $$
+declare
+  v_id uuid;
+  v_employee_id uuid := (payload->>'employee_id')::uuid;
+  v_employee_name text;
+  v_category text := coalesce(nullif(payload->>'category', ''), 'Allgemein');
+  v_note_text text := payload->>'note_text';
+  v_due_date date := nullif(payload->>'due_date', '')::date;
+begin
+  perform require_hr_admin();
+  select first_name || ' ' || last_name into v_employee_name from employees where id = v_employee_id;
+  if not found then
+    raise exception 'Mitarbeiter:in nicht gefunden.';
+  end if;
+  if coalesce(btrim(v_note_text), '') = '' then
+    raise exception 'Notiztext darf nicht leer sein.';
+  end if;
+
+  insert into employee_notes (employee_id, author_user_id, author_name, category, note_text, due_date)
+    values (v_employee_id, auth.uid(), current_actor_name(), v_category, v_note_text, v_due_date)
+    returning id into v_id;
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, target_employee_id, details)
+    values (
+      auth.uid(), current_actor_name(), 'HR-Notiz hinzugefügt', v_employee_name, v_employee_id,
+      '[' || v_category || '] ' || left(v_note_text, 200) ||
+        case when v_due_date is not null then ', Wiedervorlage am ' || v_due_date else '' end
+    );
+
+  return v_id;
+end;
+$$;
+
+-- ── HR-Notiz als erledigt markieren ───────────────────────────────────
+create or replace function complete_employee_note(payload jsonb)
+returns void language plpgsql as $$
+declare
+  v_note employee_notes%rowtype;
+  v_employee_name text;
+begin
+  perform require_hr_admin();
+  select * into v_note from employee_notes where id = (payload->>'note_id')::uuid;
+  if not found then
+    raise exception 'Notiz nicht gefunden.';
+  end if;
+  if v_note.done then
+    raise exception 'Notiz ist bereits erledigt.';
+  end if;
+  select first_name || ' ' || last_name into v_employee_name from employees where id = v_note.employee_id;
+
+  update employee_notes set done = true, done_at = now(), done_by = auth.uid() where id = v_note.id;
+
+  insert into audit_log (actor_user_id, actor_name, action, target_label, target_employee_id, details)
+    values (
+      auth.uid(), current_actor_name(), 'HR-Notiz erledigt', v_employee_name, v_note.employee_id,
+      '[' || v_note.category || '] ' || left(v_note.note_text, 200)
+    );
+end;
+$$;