Add CI workflow for backend tests using GitHub Actions

.gitea/workflows/backend-tests.yml

@@ -0,0 +1,25 @@
+name: Backend Tests
+on:
+  push:
+    paths:
+      - 'backend/**'
+  pull_request:
+    paths:
+      - 'backend/**'
+
+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: 22
+          cache: 'pnpm'
+      - name: Install dependencies
+        run: pnpm install
+      - name: Run Backend Tests
+        run: pnpm -F @memegoat/backend test