test(smoke): add smoke tests and coverage gate for backend

Signed-off-by: Noooste <83548733+Noooste@users.noreply.github.com>

.github/workflows/test.yml

@@ -0,0 +1,69 @@
+name: backend-tests
+
+on:
+  pull_request:
+    paths:
+      - 'backend/**'
+      - 'Dockerfile'
+      - 'Makefile'
+      - 'scripts/coverage-gate.sh'
+      - '.github/workflows/test.yml'
+  push:
+    branches: [main]
+
+jobs:
+  unit:
+    name: Unit tests + coverage gate
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache: true
+          cache-dependency-path: backend/go.sum
+
+      - name: Run unit tests with race detector and coverage
+        run: |
+          cd backend
+          go test -race -coverprofile=../coverage.out -coverpkg=./... ./...
+
+      - name: Enforce coverage gate
+        run: ./scripts/coverage-gate.sh coverage.out
+
+      - name: Upload coverage artifact
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage
+          path: coverage.out
+
+  smoke:
+    name: Smoke test (docker compose)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache: true
+          cache-dependency-path: backend/go.sum
+
+      - name: Run smoke test
+        run: make test-smoke
+
+      - name: Dump compose logs on failure
+        if: failure()
+        run: |
+          docker compose -p garage-ui-smoke \
+            -f backend/tests/smoke/docker-compose.test.yml logs --no-color || true
+
+      - name: Tear down compose
+        if: always()
+        run: |
+          docker compose -p garage-ui-smoke \
+            -f backend/tests/smoke/docker-compose.test.yml down -v || true