refactor(ext/sw): extract storage.ts + move itemToManifestEntry (Plan C Phase 2)

P1.9: loadDeviceSettings / loadBlacklist / saveBlacklist / saveDeviceSettings
+ itemToManifestEntry were duplicated across popup-only.ts and
content-callable.ts. Lifts the four storage helpers into service-worker/
storage.ts and itemToManifestEntry into service-worker/vault.ts.

Both router files now import from one home each. Adds storage.test.ts
covering round-trips and defaults.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

extension/src/service-worker/storage.ts

@@ -0,0 +1,25 @@
+/// Single home for chrome.storage.local reads/writes done by the service
+/// worker. Both router files (popup-only.ts and content-callable.ts) import
+/// from here — the duplicated definitions in those files were lifted out as
+/// part of Plan C Phase 2 (P1.9).
+
+import type { DeviceSettings } from '../shared/types';
+import { DEFAULT_DEVICE_SETTINGS } from '../shared/types';
+
+export async function loadDeviceSettings(): Promise<DeviceSettings> {
+  const r = await chrome.storage.local.get('relicarioSettings');
+  return (r.relicarioSettings as DeviceSettings) ?? { ...DEFAULT_DEVICE_SETTINGS };
+}
+
+export async function saveDeviceSettings(s: DeviceSettings): Promise<void> {
+  await chrome.storage.local.set({ relicarioSettings: s });
+}
+
+export async function loadBlacklist(): Promise<string[]> {
+  const r = await chrome.storage.local.get('captureBlacklist');
+  return (r.captureBlacklist as string[]) ?? [];
+}
+
+export async function saveBlacklist(list: string[]): Promise<void> {
+  await chrome.storage.local.set({ captureBlacklist: list });
+}