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.

components/reports/ReportsPageClient.tsx

@@ -18,6 +18,7 @@ import {
   MEASURE_LABELS,
   parseStatuses,
   REPORT_PRESETS,
+  sortKeysForDimension,
   STATUS_OPTIONS,
   todayIso,
   type EventGroupDimension,
@@ -86,11 +87,11 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
       if (v) sp.set(k, v);
       else sp.delete(k);
     }
-    router.push(`${pathname}?${sp.toString()}`);
+    router.push(`${pathname}?${sp.toString()}`, { scroll: false });
   }
 
   function switchMode(next: "snapshot" | "events") {
-    router.push(`${pathname}?mode=${next}`);
+    router.push(`${pathname}?mode=${next}`, { scroll: false });
   }
 
   function toggleStatus(status: string) {
@@ -106,7 +107,7 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
     sp.set("group", preset.group);
     if (preset.split) sp.set("split", preset.split);
     if (preset.eventType) sp.set("eventType", preset.eventType);
-    router.push(`${pathname}?${sp.toString()}`);
+    router.push(`${pathname}?${sp.toString()}`, { scroll: false });
   }
 
   function applySavedReport(config: Record<string, unknown>) {
@@ -115,7 +116,7 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
       if (typeof v === "string" && v) sp.set(k, v);
     }
     if (!sp.get("mode")) sp.set("mode", "snapshot");
-    router.push(`${pathname}?${sp.toString()}`);
+    router.push(`${pathname}?${sp.toString()}`, { scroll: false });
   }
 
   async function handleConfirmSaveReport() {
@@ -189,6 +190,9 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
 
   const isAverage = mode === "snapshot" && AVERAGE_MEASURES.includes(props.measure);
   const maxValue = Math.max(1, ...rows.map((r) => r.value));
+  const rawSplitKeys = Array.from(new Set(rows.flatMap((r) => r.split?.map((s) => s.key) ?? [])));
+  const splitKeys = mode === "snapshot" && props.split ? sortKeysForDimension(rawSplitKeys, props.split) : rawSplitKeys;
+  const showWeekdayMultiCountNote = mode === "snapshot" && (props.group === "weekday" || props.split === "weekday");
   const selectedStatuses = mode === "snapshot" ? parseStatuses(props.filters.status) : [];
   const statusExportLabel = selectedStatuses.length === STATUS_OPTIONS.length ? "Alle" : selectedStatuses.join(", ");
   const currentYear = new Date().getFullYear();
@@ -508,10 +512,15 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
         </div>
 
         <p className="mb-4 text-2xl font-extrabold text-ink">{totalDisplay}</p>
+        {showWeekdayMultiCountNote && (
+          <p className="mb-3 text-xs text-ink-muted">
+            Mitarbeitende mit mehreren Arbeitstagen zählen bei „Wochentag“ an jedem ihrer Arbeitstage mehrfach – Summe und Anteile ergeben daher mehr als den Gesamt-Headcount bzw. 100%.
+          </p>
+        )}
 
         {((mode === "snapshot" && props.split) || (mode === "events" && props.eventSplit)) && (
           <div className="mb-3 flex flex-wrap gap-3">
-            {Array.from(new Set(rows.flatMap((r) => r.split?.map((s) => s.key) ?? []))).map((key, i) => (
+            {splitKeys.map((key, i) => (
               <span key={key} className="flex items-center gap-1.5 text-xs text-ink-body">
                 <span className={`h-2.5 w-2.5 rounded-full ${SPLIT_COLORS[i % SPLIT_COLORS.length]}`} />
                 {key}