Consolidation pass: HR-only access, effective-dated mutations, data integrity guards, test suite

Reworks the app from a two-role (hr_admin/manager) model to a single
HR-only role gated by profiles.is_active, fixes transfer/promote/karenz/
reorg RPCs to actually defer future-dated changes via a new
pending_org_changes table instead of writing them immediately (applied
by a daily Vercel Cron route), makes reorg undo append-only instead of
deleting history, adds Karenz-return and history-date integrity guards,
deprecates the salary column, and adds explicit schema grants + perf
indexes needed to run against a fresh (non-hosted) Postgres instance.

Adds vitest unit + integration test suites (the latter against a real
local Supabase instance) covering all of the above, plus lint/typecheck/
build wiring (`npm run check`).

tests/integration/authorization.test.ts

@@ -0,0 +1,93 @@
+import { afterEach, describe, expect, it } from "vitest";
+import {
+  adminClient,
+  createBareAuthUser,
+  createHrUser,
+  deleteTestUser,
+  signInAs,
+  type TestUser,
+} from "./helpers";
+
+// HR-only access model (supabase/migrations/20260714120000_hr_only_access.sql):
+// nobody except an active, explicitly-provisioned HR user may read or write
+// anything beyond their own profile row.
+describe("HR-only access (is_hr_user gate)", () => {
+  const createdUsers: TestUser[] = [];
+
+  afterEach(async () => {
+    while (createdUsers.length) {
+      const user = createdUsers.pop()!;
+      await deleteTestUser(user);
+    }
+  });
+
+  it("a bare authenticated user (no profile row) reads zero employees, not an error", async () => {
+    const user = await createBareAuthUser();
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { data, error } = await client.from("employees").select("id");
+    expect(error).toBeNull();
+    expect(data).toEqual([]);
+  });
+
+  it("a bare authenticated user cannot insert into org reference tables", async () => {
+    const user = await createBareAuthUser();
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { error } = await client.from("divisions").insert({ org_number: "20999999", name: `Test-${user.id}` });
+    expect(error).not.toBeNull();
+  });
+
+  it("an inactive HR profile can read its own profile row", async () => {
+    const user = await createHrUser({ active: false });
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { data, error } = await client.from("profiles").select("id, is_active").eq("id", user.id);
+    expect(error).toBeNull();
+    expect(data).toHaveLength(1);
+    expect(data?.[0].is_active).toBe(false);
+  });
+
+  it("an inactive HR profile reads zero employees and cannot call mutation RPCs", async () => {
+    const user = await createHrUser({ active: false });
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { data: employees, error: readError } = await client.from("employees").select("id");
+    expect(readError).toBeNull();
+    expect(employees).toEqual([]);
+
+    const { error: rpcError } = await client.rpc("hire_employee", {
+      payload: { first_name: "X", last_name: "Y", gender: "m", birth_date: "1990-01-01", entry_date: "2020-01-01" },
+    });
+    expect(rpcError?.message).toMatch(/Nicht berechtigt/);
+  });
+
+  it("an active HR user reads the seeded employee roster", async () => {
+    const user = await createHrUser({ active: true });
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { data, error } = await client.from("employees").select("id").limit(1);
+    expect(error).toBeNull();
+    expect((data ?? []).length).toBeGreaterThan(0);
+  });
+
+  it("apply_due_pending_changes is revoked from authenticated users, even active HR", async () => {
+    const user = await createHrUser({ active: true });
+    createdUsers.push(user);
+    const client = await signInAs(user);
+
+    const { error } = await client.rpc("apply_due_pending_changes");
+    expect(error).not.toBeNull();
+  });
+
+  it("apply_due_pending_changes is callable by the service-role client", async () => {
+    const { data, error } = await adminClient.rpc("apply_due_pending_changes");
+    expect(error).toBeNull();
+    expect(typeof data).toBe("number");
+  });
+});