Phase 6/7: Reports builder and Audit log - all 7 routes now complete

Reports (§4.8):
- lib/reports.ts: generic server-side aggregation engine over 9 measures
  (Headcount, FTE, Eintritte, Austritte, Ø Bruttogehalt, Teilzeitquote,
  Ø Alter, Ø Zugehoerigkeit, Frauenanteil) x 10 group-by dimensions, with
  an optional second-dimension split (disabled for average-type
  measures) and per-row drill-down data.
- app/(app)/reports/page.tsx: reads filters from the URL, fetches the
  matching employees_directory rows server-side, aggregates in Node
  (not shipped raw to the client), computes the total.
- ReportsPageClient: measure/group/split/filter controls, 6 preset
  chips, saved-reports list (actions/reports.ts), CSV export
  (client-side blob download), stacked bars with a color-keyed legend
  when split is active, and click-to-drill-down into the underlying
  people (capped at 12, "+N weitere", linking to /employees/[id]).

Audit log (§4.9):
- app/(app)/audit/page.tsx + AuditFilters: search (target/details/actor)
  + action-type filter, paginated table with colored action badges,
  row links to the affected employee when target_employee_id is set,
  and the required "unveraenderbar" footer note.

This completes every route from the spec's information architecture:
Dashboard, Mitarbeiter:innen (list+detail), Organigramm (3 views),
Positionen & Bereiche, Berichte, Audit-Log, plus the Hire wizard and all
6 action panels reachable from them.

Final verification: clean npm run build + tsc --noEmit, then a full
browser walkthrough of all 6 authenticated routes as hr_admin (zero
console errors, zero 5xx responses) and a role-check pass as the
manager test account confirming action buttons and the "+ Neueinstellung"
button are hidden, and salary is masked as "... (ausgeblendet)" on the
Vertrag & Gehalt tab. Swept the database for leftover test data from
the debugging sessions above - none found, seed data is clean.

app/(app)/reports/page.tsx

@@ -0,0 +1,117 @@
+import { Suspense } from "react";
+import { ReportsPageClient } from "@/components/reports/ReportsPageClient";
+import {
+  aggregateReport,
+  DATE_SCOPED_MEASURES,
+  type GroupDimension,
+  type Measure,
+  type OrgLookups,
+  type ReportEmployee,
+} from "@/lib/reports";
+import { createClient } from "@/lib/supabase/server";
+import type { EmploymentStatus, EmploymentType } from "@/lib/supabase/types";
+
+type SearchParams = {
+  measure?: string;
+  group?: string;
+  split?: string;
+  division?: string;
+  location?: string;
+  status?: string;
+  employment?: string;
+  from?: string;
+  to?: string;
+};
+
+export default async function ReportsPage({ searchParams }: { searchParams: Promise<SearchParams> }) {
+  const params = await searchParams;
+  const supabase = await createClient();
+
+  const measure = (params.measure as Measure) || "headcount";
+  const group = (params.group as GroupDimension) || "division";
+  const split = (params.split as GroupDimension) || undefined;
+
+  const [{ data: divisions }, { data: departments }, { data: teams }, { data: locations }] = await Promise.all([
+    supabase.from("divisions").select("id, name").order("name"),
+    supabase.from("departments").select("id, name"),
+    supabase.from("teams").select("id, name, department_id"),
+    supabase.from("locations").select("id, name").order("name"),
+  ]);
+
+  const departmentNameById = new Map((departments ?? []).map((d) => [d.id, d.name]));
+  const lookups: OrgLookups = {
+    divisionName: new Map((divisions ?? []).map((d) => [d.id, d.name])),
+    departmentNameByTeam: new Map((teams ?? []).map((t) => [t.id, departmentNameById.get(t.department_id) ?? "Unbekannt"])),
+    teamName: new Map((teams ?? []).map((t) => [t.id, t.name])),
+    locationName: new Map((locations ?? []).map((l) => [l.id, l.name])),
+  };
+
+  let query = supabase
+    .from("employees_directory")
+    .select(
+      "id, first_name, last_name, job_title, division_id, team_id, location_id, status, employment_type, contract_type, entry_date, exit_date, weekly_hours, monthly_salary_gross, source, paygrade, birth_date, gender"
+    );
+
+  if (params.division) query = query.eq("division_id", params.division);
+  if (params.location) query = query.eq("location_id", params.location);
+  if (params.status) query = query.eq("status", params.status as EmploymentStatus);
+  if (params.employment) query = query.eq("employment_type", params.employment as EmploymentType);
+
+  const isDateScoped = DATE_SCOPED_MEASURES.includes(measure);
+  const currentYear = new Date().getFullYear();
+  const from = params.from || `${currentYear}-01-01`;
+  const to = params.to || `${currentYear}-12-31`;
+  if (isDateScoped) {
+    if (measure === "hires") query = query.gte("entry_date", from).lte("entry_date", to);
+    else query = query.gte("exit_date", from).lte("exit_date", to).not("exit_date", "is", null);
+  } else if (!params.status) {
+    query = query.in("status", ["Aktiv", "Karenz"]);
+  }
+
+  const { data: employeesData } = await query;
+  const employees = (employeesData ?? []) as ReportEmployee[];
+
+  const rows = aggregateReport(employees, measure, group, split ?? null, lookups);
+  const total = measureValueForTotal(rows, measure);
+
+  const {
+    data: { user },
+  } = await supabase.auth.getUser();
+  const { data: savedReports } = user
+    ? await supabase.from("saved_reports").select("id, name, config").eq("created_by", user.id).order("created_at", { ascending: false })
+    : { data: [] };
+
+  return (
+    <Suspense>
+      <ReportsPageClient
+        measure={measure}
+        group={group}
+        split={split ?? ""}
+        filters={{
+          division: params.division ?? "",
+          location: params.location ?? "",
+          status: params.status ?? "",
+          employment: params.employment ?? "",
+          from: params.from ?? "",
+          to: params.to ?? "",
+        }}
+        rows={rows}
+        total={total}
+        recordCount={employees.length}
+        divisions={divisions ?? []}
+        locations={locations ?? []}
+        savedReports={savedReports ?? []}
+      />
+    </Suspense>
+  );
+}
+
+function measureValueForTotal(rows: { value: number; count: number }[], measure: Measure): number {
+  if (["headcount", "fte", "hires", "exits"].includes(measure)) {
+    return rows.reduce((s, r) => s + r.value, 0);
+  }
+  // averages/ratios: weight by underlying count for a sensible overall figure
+  const totalCount = rows.reduce((s, r) => s + r.count, 0);
+  if (totalCount === 0) return 0;
+  return rows.reduce((s, r) => s + r.value * r.count, 0) / totalCount;
+}