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/api/export/events/route.ts

@@ -1,9 +1,9 @@
 import { NextResponse, type NextRequest } from "next/server";
 import { exportFilename, exportResponseHeaders, toCsv, toXlsx, type ExportColumn } from "@/lib/export";
-import { EVENT_TYPE_LABELS, type OrgLookups, type ReportEvent } from "@/lib/reports";
+import { EVENT_TYPE_LABELS, parseEventDateParam, parseEventType, type OrgLookups, type ReportEvent } from "@/lib/reports";
 import { loadEventHistory, loadOrgLookups } from "@/lib/reports-data";
+import { requireHrUser } from "@/lib/supabase/auth";
 import { createClient } from "@/lib/supabase/server";
-import type { HistoryEventType } from "@/lib/supabase/types";
 
 // Full raw event-log dump — one row per employee_history entry in the
 // selected period (default: current year), every event type unless one is
@@ -11,30 +11,21 @@ import type { HistoryEventType } from "@/lib/supabase/types";
 // placement (see loadEventHistory).
 export async function GET(request: NextRequest) {
   const supabase = await createClient();
-  const {
-    data: { user },
-  } = await supabase.auth.getUser();
-  if (!user) return NextResponse.json({ error: "Nicht angemeldet." }, { status: 401 });
-
-  const { data: profile } = await supabase.from("profiles").select("role, is_active").eq("id", user.id).maybeSingle();
-  if (profile?.role !== "hr" || profile?.is_active !== true) {
-    return NextResponse.json({ error: "Nicht berechtigt." }, { status: 403 });
-  }
+  const denied = await requireHrUser(supabase);
+  if (denied) return denied;
 
   const params = request.nextUrl.searchParams;
   const format = params.get("format") === "xlsx" ? "xlsx" : "csv";
-  const eventType = (params.get("eventType") as HistoryEventType) || undefined;
-  const from = params.get("from") ?? undefined;
-  const to = params.get("to") ?? undefined;
+  const eventType = parseEventType(params.get("eventType"));
 
   const [{ lookups }, events] = await Promise.all([
     loadOrgLookups(supabase),
     loadEventHistory(supabase, {
-      eventType,
+      eventType: eventType ?? undefined,
       division: params.get("division") ?? undefined,
       location: params.get("location") ?? undefined,
-      from,
-      to,
+      from: parseEventDateParam(params.get("from")),
+      to: parseEventDateParam(params.get("to")),
     }),
   ]);