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/shell/NotesBell.tsx

@@ -0,0 +1,89 @@
+"use client";
+
+import { Bell } from "lucide-react";
+import Link from "next/link";
+import { useRouter } from "next/navigation";
+import { useEffect, useRef, useState } from "react";
+import { completeEmployeeNote } from "@/actions/employees";
+import { useToast } from "@/components/ui/Toast";
+import { NOTE_CATEGORY_STYLES } from "@/lib/colors";
+import { fmtDate } from "@/lib/format";
+import type { OpenNote } from "@/lib/notes";
+
+// Click-outside mechanics borrowed from CountryPicker (useRef + mousedown
+// listener) — without its draft-text reset, which has no equivalent here.
+export function NotesBell({ notes }: { notes: OpenNote[] }) {
+  const { showToast } = useToast();
+  const router = useRouter();
+  const [open, setOpen] = useState(false);
+  const [completingId, setCompletingId] = useState<string | null>(null);
+  const containerRef = useRef<HTMLDivElement>(null);
+
+  useEffect(() => {
+    function onClickOutside(e: MouseEvent) {
+      if (containerRef.current && !containerRef.current.contains(e.target as Node)) {
+        setOpen(false);
+      }
+    }
+    document.addEventListener("mousedown", onClickOutside);
+    return () => document.removeEventListener("mousedown", onClickOutside);
+  }, []);
+
+  async function handleComplete(note: OpenNote) {
+    setCompletingId(note.id);
+    const result = await completeEmployeeNote({ note_id: note.id, employee_id: note.employee_id });
+    setCompletingId(null);
+    if (result.success) {
+      showToast("Notiz erledigt.");
+      router.refresh();
+    } else {
+      showToast(result.error ?? "Fehler beim Speichern.", "error");
+    }
+  }
+
+  return (
+    <div ref={containerRef} className="relative">
+      <button type="button" onClick={() => setOpen((o) => !o)} aria-label="Meine Notizen" className="relative rounded p-1.5 text-ink-muted hover:bg-surface">
+        <Bell className="h-4 w-4" />
+        {notes.length > 0 && (
+          <span className="absolute -right-1 -top-1 flex h-4 min-w-4 items-center justify-center rounded-full bg-danger-solid px-1 text-[10px] font-bold text-white">
+            {notes.length}
+          </span>
+        )}
+      </button>
+
+      {open && (
+        <div className="absolute right-0 z-20 mt-2 max-h-[28rem] w-96 overflow-y-auto rounded border border-border bg-white shadow-lg">
+          <div className="border-b border-border px-4 py-2.5 text-xs font-bold uppercase tracking-wide text-ink-muted">Meine Notizen ({notes.length})</div>
+          {notes.length === 0 ? (
+            <p className="px-4 py-6 text-center text-sm text-ink-muted">Keine offenen Notizen.</p>
+          ) : (
+            <ul className="divide-y divide-border">
+              {notes.map((n) => (
+                <li key={n.id} className="px-4 py-3">
+                  <div className="flex flex-wrap items-center gap-2">
+                    <span className={`rounded-full px-2 py-0.5 text-xs font-semibold ${NOTE_CATEGORY_STYLES[n.category]}`}>{n.category}</span>
+                    <Link href={`/employees/${n.employee_id}`} className="text-sm font-semibold text-ink hover:text-brand-700 hover:underline">
+                      {n.employeeName}
+                    </Link>
+                    <span className="text-xs text-ink-muted">{fmtDate(n.created_at)}</span>
+                  </div>
+                  <p className="mt-1 text-sm text-ink-body">{n.note_text}</p>
+                  {n.due_date && <p className="mt-1 text-xs text-warning-text">🔔 fällig {fmtDate(n.due_date)}</p>}
+                  <button
+                    type="button"
+                    onClick={() => handleComplete(n)}
+                    disabled={completingId === n.id}
+                    className="mt-2 text-xs font-semibold text-success-text hover:underline disabled:opacity-50"
+                  >
+                    ✓ Erledigt
+                  </button>
+                </li>
+              ))}
+            </ul>
+          )}
+        </div>
+      )}
+    </div>
+  );
+}