fix(13-02): eliminate all ESLint violations — pnpm lint exits 0

- eslint.config.js: disable React Compiler rules (v7 flat.recommended enables
  them; codebase does not use the Compiler); add e2e/ to disableTypeChecked
  block; promote exhaustive-deps to error
- API broker: remove redundant as-casts (outboxWorker, poller, reminderScheduler,
  expand, sync, vevent, spike); add targeted ical.js no-unsafe-assignment/argument
  disables with justifying comments inside try blocks
- API routes/sse.ts: fix no-misused-promises on async writeSSE callback with
  void+IIFE+catch pattern
- API routes/lists.ts: let → const for updateValues
- API tests: remove unused imports (beforeEach, eq, vi); rename unused vars
  with _ prefix; remove unused lastActiveId assignment
- PWA components: void navigate() and void queryClient.invalidateQueries() on
  all fire-and-forget call sites; fix CalendarShell explicit-type-casts;
  Couldn't → HTML entity
- PWA test files: as unknown as Response for partial mock objects; string | null
  type annotation on mockLastSyncedUid; remove async from test callbacks without
  await; act(() => {}) not await act(async () => {}) for sync ops
- sw.ts: restructure Notification.data?.url access as let+if so disable
  comments land on the exact violation lines; void self.skipWaiting()

apps/api/src/routes/lists.ts

@@ -601,7 +601,7 @@ listItemsRouter.patch('/:itemId', zValidator('json', patchItemSchema), async (c)
     }
 
     // Build the update payload — single-field write with updatedAt=NOW()
-    let updateValues: {
+    const updateValues: {
       checked?: boolean
       text?: string
       rank?: string