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.

app/(app)/orgchart/page.tsx

@@ -1,42 +1,55 @@
+import { Suspense } from "react";
 import { OrgChartClient } from "@/components/orgchart/OrgChartClient";
+import { todayIso } from "@/lib/format";
+import { loadOrgAsOf } from "@/lib/orgchart-data";
 import { loadOpenPositions } from "@/lib/positions";
+import { parseIsoDateParam } from "@/lib/reports";
 import { createClient } from "@/lib/supabase/server";
 
-export default async function OrgChartPage() {
+type SearchParams = { asOf?: string; focus?: string };
+
+const UUID = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+export default async function OrgChartPage({ searchParams }: { searchParams: Promise<SearchParams> }) {
+  const params = await searchParams;
+  const today = todayIso();
+  const asOf = parseIsoDateParam(params.asOf) ?? today;
+  // Only ever used to match against ids already on the page, but validated
+  // so a junk value can't reach the client as an arbitrary string.
+  const focusId = params.focus && UUID.test(params.focus) ? params.focus : null;
+
   const supabase = await createClient();
 
-  const [
-    { data: employees },
-    { data: divisions },
-    { data: departments },
-    { data: teams },
-    openPositions,
-    { data: reorgScenarios },
-  ] = await Promise.all([
-    supabase
-      .from("employees")
-      .select("id, personnel_number, first_name, last_name, job_title, manager_id, team_id, division_id, is_lead, org_level")
-      .in("status", ["Aktiv", "Karenz"]),
-    supabase.from("divisions").select("*").order("name"),
-    supabase.from("departments").select("*"),
-    supabase.from("teams").select("*"),
-    loadOpenPositions(supabase),
-    supabase
-      .from("reorg_scenarios")
-      .select("id, name, effective_date, applied, applied_at")
-      .eq("applied", true)
-      .order("applied_at", { ascending: false })
-      .limit(5),
-  ]);
+  const [org, { data: divisions }, { data: departments }, { data: teams }, openPositions, { data: reorgScenarios }] =
+    await Promise.all([
+      loadOrgAsOf(supabase, asOf),
+      supabase.from("divisions").select("*").order("name"),
+      supabase.from("departments").select("*"),
+      supabase.from("teams").select("*"),
+      loadOpenPositions(supabase),
+      supabase
+        .from("reorg_scenarios")
+        .select("id, name, effective_date, applied, applied_at")
+        .eq("applied", true)
+        .order("applied_at", { ascending: false })
+        .limit(5),
+    ]);
 
   return (
-    <OrgChartClient
-      employees={employees ?? []}
-      divisions={divisions ?? []}
-      departments={departments ?? []}
-      teams={teams ?? []}
-      openPositions={openPositions}
-      reorgScenarios={reorgScenarios ?? []}
-    />
+    <Suspense>
+      <OrgChartClient
+        employees={org.employees}
+        divisions={divisions ?? []}
+        departments={departments ?? []}
+        teams={teams ?? []}
+        openPositions={openPositions}
+        reorgScenarios={reorgScenarios ?? []}
+        asOf={asOf}
+        today={today}
+        projectedCount={org.projectedCount}
+        historyStartsAt={org.historyStartsAt}
+        focusId={focusId}
+      />
+    </Suspense>
   );
 }