feat(18-03): route all-day reminder TZ through stored household_timezone

- reminderScheduler.ts: add import { getHouseholdTimezone } from '../lib/householdTimezone.js'
  and replace bare process.env.TZ ?? Intl... at line 247 with await getHouseholdTimezone(db)
- outboxWorker.ts: add same import and replace BOTH bare tz lookups at the update-branch
  (~line 501) and create-branch (~line 607) with await getHouseholdTimezone(db)
- D-05 satisfied: all three all-day sites now read from the single stored accessor
- D-06 satisfied: getHouseholdTimezone falls back to process.env.TZ → Intl when unset;
  existing process.env.TZ-pinned tests pass unchanged
- D-07 satisfied: eventDateTime.ts and hydrateEvents.ts are not modified
- outboxWorker.test.ts: update wireMockChain() to handle app_config table with where().limit()
  chain returning empty rows (D-06 fallback), so existing CAL-13 all-day test stays green
- reminderScheduler.test.ts: update mockTwoQueries to mock the new third db.select() call
  (getHouseholdTimezone) returning no row (D-06 fallback), keeping all 37 existing tests green
- All 76 broker tests pass; tsc --noEmit clean

apps/api/tests/broker/outboxWorker.test.ts

@@ -142,6 +142,8 @@ function wireMockChain() {
   // mockFromFn differentiates by table argument using Symbol.for('drizzle:Name'):
   // - memberCredentials → returns FAKE_CRED_ROW (so loadClientForUser succeeds by default)
   // - calendarEvents → returns mockWhereCalEvents (etag re-read for WR-02)
+  // - app_config → returns empty row array (D-06 fallback: no stored TZ → Intl fallback)
+  //   getHouseholdTimezone(db) chain: .from(appConfig).where(...).limit(1) → []
   // - calendarOutbox (and anything else) → returns mockWherePending (pending-rows + sibling-status)
   // JSON.stringify throws on circular Drizzle table structures; use Symbol identity instead.
   mockFromFn.mockImplementation((table: unknown) => {
@@ -160,6 +162,13 @@ function wireMockChain() {
         }),
       };
     }
+    if (tableName === 'app_config') {
+      // D-06: default = no stored timezone row → getHouseholdTimezone falls back to
+      // process.env.TZ → Intl. The where().limit(1) chain must be mockable.
+      // Plan 18-03 tests override this via wireMockChainWithTz to inject a stored zone.
+      const limitFn = vi.fn().mockResolvedValue([]); // no stored row → D-06 fallback
+      return { where: vi.fn().mockReturnValue({ limit: limitFn }) };
+    }
     return { where: mockWherePending };
   });
   mockWhereCalEvents.mockImplementation(() => Promise.resolve([]));