feat: Complete backend CI/CD workflow setup

- Add comprehensive GitHub Actions workflows for Go backend
- Build workflow with binary compilation and attestation
- Test workflow with coverage reporting and race detection
- Lint workflow with golangci-lint and security scanning
- Docker build workflow with multi-architecture support
- Deploy workflow for production deployment
- Security workflow with vulnerability scanning
- All workflows follow Single Responsibility Principle
- Use semantic versioning and latest action versions
- Enable security features: OIDC auth, attestations, minimal permissions

.github/workflows/build.yml

@@ -16,10 +16,10 @@ jobs:
       id-token: write
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: "1.25"
           cache: true
@@ -39,7 +39,7 @@ jobs:
         run: ./bin/tercul-backend --help || echo "Binary built successfully"
 
       - name: Upload build artifacts
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: tercul-backend-binary
           path: bin/

.github/workflows/deploy.yml

@@ -20,7 +20,7 @@ jobs:
 
     steps:
       - name: Check out code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Extract version
         id: version

.github/workflows/docker-build.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Check out code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3

.github/workflows/lint.yml

@@ -12,10 +12,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: "1.25"
           cache: true

.github/workflows/security.yml

@@ -20,7 +20,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3
@@ -30,7 +30,7 @@ jobs:
           # queries: security-extended
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: "1.25"
           cache: true

.github/workflows/test.yml

@@ -32,10 +32,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: "1.25"
           cache: true
@@ -58,7 +58,7 @@ jobs:
           echo "- **Go Version**: 1.25" >> $GITHUB_STEP_SUMMARY
 
       - name: Upload coverage reports
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: coverage-report
           path: |
@@ -96,10 +96,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Go ${{ matrix.go-version }}
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: ${{ matrix.go-version }}
           cache: true