refactor(web): sweep 8 test files to use pageUrlModule() (#375)

Centralizes the inline { page: { get url() { return state.pageUrl } } }
mock shape via test-utils/mocks/appState.ts. The vi.hoisted state
declaration remains per-file (vitest mock-hoisting requires module-
level declaration). Adds a $test-utils alias to svelte.config.js so
the helper can be imported without ../../../ chains.

SKIPPED (mock exposes more than url):
- Shell.test.ts, MobileNavDrawer.test.ts, admin.test.ts: static
  page: { url: ... } shape, no hoisted state to centralize.
- album.test.ts, artist.test.ts: page exposes both params and url.
- playlist.test.ts, reset-password.test.ts: page exposes params only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/svelte.config.js

@@ -13,6 +13,12 @@ export default {
     }),
     files: {
       assets: 'static'
+    },
+    alias: {
+      // test-only helper barrel; resolves the same way $lib does so test
+      // files can import shared mock factories without ../../../ chains.
+      '$test-utils': 'src/test-utils',
+      '$test-utils/*': 'src/test-utils/*'
     }
   }
 };