feat(03-10): fail closed on bad credentials + fix backoff index + explicit randomUUID (CR-03, WR-01, WR-08)

- outboxWorker: remove empty-credential fallback; let loadClientForUser throw on error (CR-03)
- outboxWorker: fix backoff index from nextAttemptCount to row.attemptCount so first retry waits 15s not 60s (WR-01)
- events.ts: replace bare crypto.randomUUID() with import { randomUUID } from 'node:crypto' on all three handlers (WR-08)

apps/api/src/routes/events.ts

@@ -21,6 +21,7 @@
  * Mounted under /api/* in index.ts — behind oidcAuthMiddleware.
  */
 
+import { randomUUID } from 'node:crypto'
 import { Hono } from 'hono'
 import { zValidator } from '@hono/zod-validator'
 import { z } from 'zod'
@@ -253,7 +254,7 @@ eventsRouter.post('/create', zValidator('json', eventFieldsSchema), async (c) =>
     }
 
     // Generate a UID for the new event (Node.js 22 built-in)
-    const uid = `${crypto.randomUUID()}@familysync`
+    const uid = `${randomUUID()}@familysync`
 
     // Enqueue the outbox row (pending) — the worker builds the VEVENT and calls Fastmail.
     await db.insert(calendarOutbox).values({
@@ -325,8 +326,8 @@ eventsRouter.patch('/:uid/edit', zValidator('json', eventFieldsSchema), async (c
 
     if (isCalendarMove) {
       // D-04: edit-as-move — insert delete+create pair in one transaction (D-04 / Pitfall 5)
-      const newUid = `${crypto.randomUUID()}@familysync`
-      const groupId = crypto.randomUUID()
+      const newUid = `${randomUUID()}@familysync`
+      const groupId = randomUUID()
 
       await db.transaction(async (tx) => {
         // Delete from old calendar