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.

lib/format.ts

@@ -1,14 +1,53 @@
-const dateFormatter = new Intl.DateTimeFormat("de-AT", {
+// This app stores dates as date-only strings ("YYYY-MM-DD") and timestamps as
+// timestamptz, and is used from a single timezone. Every conversion here is
+// pinned to Europe/Vienna rather than the runtime's zone: the server renders
+// in UTC (Docker/Vercel) while the browser renders in Vienna, so an unpinned
+// formatter produces a different day on each side — wrong dates for the user
+// near midnight, and a React hydration mismatch.
+const TIMEZONE = "Europe/Vienna";
+
+const dateTimeFormatter = new Intl.DateTimeFormat("de-AT", {
   day: "2-digit",
   month: "2-digit",
   year: "numeric",
+  timeZone: TIMEZONE,
 });
 
+// en-CA formats as "YYYY-MM-DD", which is the shape the rest of the app and
+// the database speak.
+const isoFormatter = new Intl.DateTimeFormat("en-CA", {
+  day: "2-digit",
+  month: "2-digit",
+  year: "numeric",
+  timeZone: TIMEZONE,
+});
+
+const DATE_ONLY = /^\d{4}-\d{2}-\d{2}$/;
+
+// Today in Vienna. Deliberately not new Date().toISOString().slice(0, 10):
+// that is the *UTC* date, which for part of every day is already tomorrow
+// relative to Austria.
+export function todayIso(): string {
+  return isoFormatter.format(new Date());
+}
+
+// Normalizes either input to a "YYYY-MM-DD" string. A date-only string is
+// returned as-is — parsing it into a Date first would anchor it to UTC
+// midnight and shift it in any negative-offset zone.
+export function toIsoDate(value: string | Date): string {
+  if (typeof value === "string") return DATE_ONLY.test(value) ? value : isoFormatter.format(new Date(value));
+  return isoFormatter.format(value);
+}
+
 export function fmtDate(date: string | Date | null | undefined): string {
   if (!date) return "–";
+  if (typeof date === "string" && DATE_ONLY.test(date)) {
+    const [year, month, day] = date.split("-");
+    return `${day}.${month}.${year}`;
+  }
   const d = typeof date === "string" ? new Date(date) : date;
   if (Number.isNaN(d.getTime())) return "–";
-  return dateFormatter.format(d);
+  return dateTimeFormatter.format(d);
 }
 
 export function initials(firstName: string, lastName: string): string {
@@ -17,24 +56,37 @@ export function initials(firstName: string, lastName: string): string {
   return `${a}${b}`;
 }
 
+// "Dr. Max Mustermann, MSc MBA" — prefix titles precede the name, suffix
+// titles follow after a comma, both space-joined in the stored order.
+export function fmtFullName(
+  firstName: string,
+  lastName: string,
+  titlePrefix: string[] | null | undefined,
+  titleSuffix: string[] | null | undefined
+): string {
+  const prefix = titlePrefix && titlePrefix.length > 0 ? `${titlePrefix.join(" ")} ` : "";
+  const suffix = titleSuffix && titleSuffix.length > 0 ? `, ${titleSuffix.join(" ")}` : "";
+  return `${prefix}${firstName} ${lastName}${suffix}`;
+}
+
+// Whole years between two ISO dates. Compares the "MM-DD" tails as strings,
+// which is exact and needs no Date arithmetic at all.
+export function yearsBetweenIso(from: string, to: string): number {
+  const years = Number(to.slice(0, 4)) - Number(from.slice(0, 4));
+  return to.slice(5) < from.slice(5) ? years - 1 : years;
+}
+
 export function fmtAge(birthDate: string | Date): number {
-  const d = typeof birthDate === "string" ? new Date(birthDate) : birthDate;
-  const today = new Date();
-  let age = today.getFullYear() - d.getFullYear();
-  const hasHadBirthdayThisYear =
-    today.getMonth() > d.getMonth() ||
-    (today.getMonth() === d.getMonth() && today.getDate() >= d.getDate());
-  if (!hasHadBirthdayThisYear) age -= 1;
-  return age;
+  return yearsBetweenIso(toIsoDate(birthDate), todayIso());
 }
 
 export function tenure(entryDate: string | Date, endDate?: string | Date | null): string {
-  const start = typeof entryDate === "string" ? new Date(entryDate) : entryDate;
-  const end = endDate ? (typeof endDate === "string" ? new Date(endDate) : endDate) : new Date();
+  const start = toIsoDate(entryDate);
+  const end = endDate ? toIsoDate(endDate) : todayIso();
 
-  let years = end.getFullYear() - start.getFullYear();
-  let months = end.getMonth() - start.getMonth();
-  if (end.getDate() < start.getDate()) months -= 1;
+  let years = Number(end.slice(0, 4)) - Number(start.slice(0, 4));
+  let months = Number(end.slice(5, 7)) - Number(start.slice(5, 7));
+  if (Number(end.slice(8, 10)) < Number(start.slice(8, 10))) months -= 1;
   if (months < 0) {
     years -= 1;
     months += 12;
@@ -47,8 +99,16 @@ export function tenure(entryDate: string | Date, endDate?: string | Date | null)
   return yearPart || monthPart || "unter 1 Monat";
 }
 
-export function daysBetween(a: string | Date, b: string | Date = new Date()): number {
-  const start = typeof a === "string" ? new Date(a) : a;
-  const end = typeof b === "string" ? new Date(b) : b;
-  return Math.round((end.getTime() - start.getTime()) / (1000 * 60 * 60 * 24));
+// Anchored at UTC midnight on both sides so the difference is a whole number
+// of calendar days regardless of DST transitions in between.
+export function daysBetweenIso(from: string, to: string = todayIso()): number {
+  const start = Date.parse(`${from}T00:00:00Z`);
+  const end = Date.parse(`${to}T00:00:00Z`);
+  return Math.round((end - start) / 86_400_000);
+}
+
+export function addDaysIso(iso: string, days: number): string {
+  const d = new Date(`${iso}T00:00:00Z`);
+  d.setUTCDate(d.getUTCDate() + days);
+  return d.toISOString().slice(0, 10);
 }