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)/page.tsx

@@ -1,12 +1,9 @@
 import Link from "next/link";
 import { DraftsCard } from "@/components/dashboard/DraftsCard";
 import { actionBadgeStyle } from "@/lib/colors";
-import { fmtDate } from "@/lib/format";
+import { addDaysIso, fmtDate, todayIso } from "@/lib/format";
 import { createClient } from "@/lib/supabase/server";
-
-function isoDate(d: Date): string {
-  return d.toISOString().slice(0, 10);
-}
+import { fetchAllRows } from "@/lib/supabase/query";
 
 const TONE_TEXT: Record<string, string> = {
   default: "text-ink",
@@ -45,13 +42,15 @@ export default async function DashboardPage() {
         .order("updated_at", { ascending: false })
     : { data: [] };
 
-  const today = new Date();
-  const todayIso = isoDate(today);
-  const yearStart = isoDate(new Date(today.getFullYear(), 0, 1));
-  const yearEnd = isoDate(new Date(today.getFullYear(), 11, 31));
-  const in60 = new Date(today);
-  in60.setDate(in60.getDate() + 60);
-  const in60Iso = isoDate(in60);
+  // Built as strings, not by round-tripping a local Date through
+  // toISOString(): in any positive-offset zone new Date(year, 0, 1) is still
+  // the previous year in UTC, which shifted the whole YTD window a day early
+  // and dropped 31 December from it entirely.
+  const today = todayIso();
+  const year = today.slice(0, 4);
+  const yearStart = `${year}-01-01`;
+  const yearEnd = `${year}-12-31`;
+  const in60Iso = addDaysIso(today, 60);
 
   const [
     activeCountRes,
@@ -59,9 +58,9 @@ export default async function DashboardPage() {
     hiresYtdRes,
     exitsYtdRes,
     openPositionsRes,
-    fteRowsRes,
+    fteRows,
     divisionsRes,
-    headcountRowsRes,
+    headcountRows,
     upcomingHiresRes,
     upcomingExitsRes,
     upcomingReturnsRes,
@@ -80,27 +79,27 @@ export default async function DashboardPage() {
       .gte("exit_date", yearStart)
       .lte("exit_date", yearEnd),
     supabase.from("positions").select("id", { count: "exact", head: true }).eq("status", "open"),
-    supabase.from("employees").select("weekly_hours").in("status", ["Aktiv", "Karenz"]),
+    fetchAllRows(() => supabase.from("employees").select("weekly_hours").in("status", ["Aktiv", "Karenz"]).order("id")),
     supabase.from("divisions").select("id, name"),
-    supabase.from("employees").select("division_id").in("status", ["Aktiv", "Karenz"]),
+    fetchAllRows(() => supabase.from("employees").select("division_id").in("status", ["Aktiv", "Karenz"]).order("id")),
     supabase
       .from("employees")
       .select("id, first_name, last_name, entry_date")
       .eq("status", "Geplant")
-      .gte("entry_date", todayIso)
+      .gte("entry_date", today)
       .lte("entry_date", in60Iso),
     supabase
       .from("employees")
       .select("id, first_name, last_name, exit_date")
       .not("exit_date", "is", null)
-      .gte("exit_date", todayIso)
+      .gte("exit_date", today)
       .lte("exit_date", in60Iso),
     supabase
       .from("employees")
       .select("id, first_name, last_name, karenz_return_date")
       .eq("status", "Karenz")
       .not("karenz_return_date", "is", null)
-      .gte("karenz_return_date", todayIso)
+      .gte("karenz_return_date", today)
       .lte("karenz_return_date", in60Iso),
     supabase
       .from("employee_history")
@@ -110,10 +109,10 @@ export default async function DashboardPage() {
       .limit(10),
   ]);
 
-  const fte = (fteRowsRes.data ?? []).reduce((sum, row) => sum + Number(row.weekly_hours), 0) / 38.5;
+  const fte = fteRows.reduce((sum, row) => sum + Number(row.weekly_hours), 0) / 38.5;
 
   const headcountByDivision = new Map<string, number>();
-  for (const row of headcountRowsRes.data ?? []) {
+  for (const row of headcountRows) {
     if (!row.division_id) continue;
     headcountByDivision.set(row.division_id, (headcountByDivision.get(row.division_id) ?? 0) + 1);
   }