test(18): make timezone e2e deterministic and align with WR-01 fix

The timezone-verify spec assumed a first-run (unset) starting state, but
e2e global-setup truncated only the list/event tables — never app_config —
so a prior run's saved household_timezone leaked across runs. Clear that key
in global-setup so the spec always starts from isExplicitlySet:false.

Also repurpose the stale "Save disabled when unchanged" assertion: after the
WR-01 fix, first-run Save is correctly ENABLED when the input matches the
displayed default (saving confirms the detected zone). The disabled-when-
unchanged-and-explicit case remains covered by the persist-across-reload test.

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

apps/pwa/e2e/global-setup.ts

@@ -109,6 +109,13 @@ export default async function globalSetup(): Promise<void> {
     await conn.execute('TRUNCATE TABLE calendar_events');
     await conn.execute('SET FOREIGN_KEY_CHECKS=1');
 
+    // Phase 18: clear any stored household timezone so the timezone spec always
+    // starts from the first-run (isExplicitlySet:false) state. app_config is NOT
+    // truncated above (it can hold other non-test config), so delete only this key.
+    // Without this, a prior run's saved value leaks across runs and makes the
+    // first-run / persist-across-reload timezone assertions non-deterministic.
+    await conn.execute("DELETE FROM app_config WHERE `key` = 'household_timezone'");
+
     // Seed the dev-bypass admin user row for id=1 (D-01 dev note, Phase 10).
     // DEV_USER (id=1) is injected by devBypass.ts WITHOUT a DB upsert, so the users table
     // has no row for id=1 by default. requireAdmin (Plan 02) does a DB lookup and would 403