Add Gitea Actions workflow to run tests on every push

Self-hosted Gitea runner picks up `.gitea/workflows/test.yml`. The job
installs deps with the committed pnpm-lock, regenerates the Prisma
client, then runs the backend Jest suite and the frontend Vitest suite
as separate steps so a failure points at the right package. Tests mock
Prisma so no database is needed in CI.

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

.gitea/workflows/test.yml

@@ -0,0 +1,32 @@
+name: Tests
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 9
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Generate Prisma client
+        run: pnpm --filter tehriehlbudget-backend exec prisma generate
+
+      - name: Backend tests (Jest)
+        run: pnpm test:backend
+
+      - name: Frontend tests (Vitest)
+        run: pnpm test:frontend