fix: 2026-06-09 full-codebase audit hardening

Validation: shared NaN-guarded Zod coercion helpers in schemas/common.ts replace
the raw number|string transform idiom across every schema (the root-cause NaN bug
class); emailOrEmpty + lenient isoDateString/timeString.

Security: roles privilege-escalation closed; refresh-token family revocation on
reuse; TOTP uses config params; read endpoints permission-guarded; received-invoices
gross VAT on all paths; orders-pdf custom-items authz.

Concurrency: $queryRaw SELECT...FOR UPDATE locks in ascending-id order (warehouse
confirm/cancel, attendance lockUserRow); uniqueness checks moved into create
transactions (TOCTOU -> 409); deterministic id tiebreak on second-precision
timestamp ordering (plan resolveCell/resolveGrid, warehouse FIFO).

Frontend: Rules-of-Hooks fixed across ~14 pages + PlanCellModal; UTC-date persisted
fields; dashboard invalidation gaps; stale-closure confirm bugs.

Tooling/tests: ESLint flat config (react-hooks/rules-of-hooks = error) + Prettier;
tsconfig.test.json so tsc -b type-checks the tests; removed 3 dead deps; npm audit
fix (8 -> 3). Suite 195 -> 247 (happy-path auth, FIFO oldest-first, flakiness fixes),
isolated on app_test via .env.test with a hard-throw setup guard.

Gates: tsc 0 | build 0 | vitest 247/247 | eslint 0 errors.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/__tests__/received-invoices-vat.test.ts

@@ -23,4 +23,29 @@ describe("vatFromGross (VAT contained in a gross total)", () => {
   it("returns 0 for a zero amount", () => {
     expect(vatFromGross(0, 21)).toBe(0);
   });
+
+  it("rounds the cent UP when the raw VAT's third decimal forces a carry", () => {
+    // 115.50 @ 21% -> raw 20.045454...  the third decimal (5) rounds the cent
+    // up to 20.05. Pinned EXACTLY (not toBeCloseTo) so a truncate-instead-of-
+    // round regression (which would yield 20.04) fails.
+    expect(vatFromGross(115.5, 21)).toBe(20.05);
+    // 95.70 @ 21% -> raw 16.609090...  rounds up to 16.61.
+    expect(vatFromGross(95.7, 21)).toBe(16.61);
+  });
+
+  it("rounds the cent DOWN when below the half-cent", () => {
+    // 100.40 @ 21% -> raw 17.424793...  rounds down to 17.42.
+    expect(vatFromGross(100.4, 21)).toBe(17.42);
+  });
+
+  it("pins the result to the exact stored 2-dp value (not just close)", () => {
+    // The DB column is Decimal(_, 2). vatFromGross must already return a value
+    // with no third-decimal float drift. Strict equality + a 2-dp self-check,
+    // NOT toBeCloseTo, so a 3-dp regression (e.g. 210.0000001) would fail.
+    const v = vatFromGross(1210, 21);
+    expect(v).toBe(210); // exact, not ~210
+    expect(v).toBe(Math.round(v * 100) / 100); // genuinely 2-dp clean
+    // The real-world figure too: pinned exactly, replacing the toBeCloseTo above.
+    expect(vatFromGross(22542.91, 21)).toBe(3912.41);
+  });
 });