chore: Migrate to vitest (#12272)

* wip

* Remove obsolete snapshots

* simplify

* chore(test): Convert mocks to TypeScript and tighten fetch mock types

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

* Remove unneccessary patches

* Migrate to msw instead of custom fetch mock

* Address PR review comments

- Split chained vi.useFakeTimers().setSystemTime() into separate calls.
- Switch test setup to dynamic imports so EventEmitter.defaultMaxListeners
  assignment runs before module init (static imports were hoisted above it).
- Drop redundant NODE_ENV guard in monkeyPatchSequelizeErrorsForJest; its
  sole caller already gates on env.isTest.

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

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -34,6 +34,7 @@ jobs:
             config:
               - '.github/**'
               - 'vite.config.ts'
+              - 'vitest.config.ts'
             server:
               - 'server/**'
               - 'shared/**'
@@ -82,15 +83,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: ./.github/actions/install
-      - name: Restore Jest transform cache
-        uses: actions/cache@v4
-        with:
-          path: /tmp/jest_runner
-          key: jest-${{ matrix.test-group }}-${{ hashFiles('.babelrc', '.jestconfig.json', 'yarn.lock', 'app/**/*.ts', 'app/**/*.tsx', 'shared/**/*.ts', 'shared/**/*.tsx') }}
-          restore-keys: |
-            jest-${{ matrix.test-group }}-${{ hashFiles('.babelrc', '.jestconfig.json', 'yarn.lock') }}-
-            jest-${{ matrix.test-group }}-
-      - run: yarn test:${{ matrix.test-group }} --cacheDirectory=/tmp/jest_runner
+      - run: yarn test:${{ matrix.test-group }}
 
   test-server:
     needs: changes
@@ -118,17 +111,9 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: ./.github/actions/install
-      - name: Restore Jest transform cache
-        uses: actions/cache@v4
-        with:
-          path: /tmp/jest_runner
-          key: jest-server-${{ matrix.shard }}-${{ hashFiles('.babelrc', '.jestconfig.json', 'yarn.lock', 'server/**/*.ts', 'shared/**/*.ts', 'plugins/**/*.ts') }}
-          restore-keys: |
-            jest-server-${{ matrix.shard }}-${{ hashFiles('.babelrc', '.jestconfig.json', 'yarn.lock') }}-
-            jest-server-${{ matrix.shard }}-
       - run: yarn sequelize db:migrate
       - name: Run server tests
-        run: yarn test:server --maxWorkers=2 --shard=${{ matrix.shard }}/4 --cacheDirectory=/tmp/jest_runner
+        run: yarn test:server --maxWorkers=2 --shard=${{ matrix.shard }}/4
 
   bundle-size:
     needs: changes