fix: 恢复backend-ci.yml

.github/workflows/backend-ci.yml

+name: CI
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+          check-latest: false
+          cache: true
+      - name: Verify Go version
+        run: |
+          go version | grep -q 'go1.25.7'
+      - name: Unit tests
+        working-directory: backend
+        run: make test-unit
+      - name: Integration tests
+        working-directory: backend
+        run: make test-integration
+
+  golangci-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+          check-latest: false
+          cache: true
+      - name: Verify Go version
+        run: |
+          go version | grep -q 'go1.25.7'
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: v2.7
+          args: --timeout=5m
+          working-directory: backend
\ No newline at end of file