refactor: reorganize CI/CD pipelines into separate workflow files

BREAKING CHANGE: Monolithic ci.yml split into focused pipeline files

## Pipeline Reorganization

Split single CI/CD pipeline into 7 specialized workflows:

1. **lint.yml** - Code quality checks (Black, Ruff, MyPy)
2. **test.yml** - Test suite with coverage reporting
3. **security.yml** - Security scanning (Bandit)
4. **build.yml** - Docker image builds and registry push
5. **deploy-staging.yml** - Staging environment deployment
6. **deploy-production.yml** - Production deployment (tags only)
7. **docs-generation.yml** - Scheduled documentation generation

## Benefits

- **Modularity**: Each pipeline has single responsibility
- **Performance**: Workflows run independently, faster feedback
- **Clarity**: Easier to understand and maintain
- **Flexibility**: Trigger pipelines independently
- **Debugging**: Isolated failures easier to diagnose

## Dockerfile Improvements

- Fix FROM AS casing (was 'as', now 'AS') in all Dockerfiles
- Resolves Docker build warnings
- Improves consistency across build files

## Documentation

- Added .gitea/workflows/README.md with:
  - Workflow descriptions and triggers
  - Dependency diagram
  - Environment variables reference
  - Troubleshooting guide
  - Best practices

## Migration Notes

- Old monolithic pipeline backed up as ci.yml.old
- All triggers preserved from original pipeline
- No changes to build or deploy logic
- Same environment variables and secrets required

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitea/workflows/deploy-production.yml

@@ -0,0 +1,50 @@
+# Deploy to Production Environment
+
+name: Deploy Production
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+env:
+  REGISTRY: ${{ vars.PACKAGES_REGISTRY }}
+  IMAGE_NAME: ${{ gitea.repository }}
+
+jobs:
+  deploy-production:
+    name: Deploy to Production
+    runs-on: ubuntu-latest
+    environment:
+      name: production
+      url: https://docs.company.local
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up kubectl
+        uses: azure/setup-kubectl@v3
+        with:
+          version: 'latest'
+
+      - name: Configure kubectl
+        run: |
+          echo "${{ secrets.KUBE_CONFIG_PRODUCTION }}" > kubeconfig
+          export KUBECONFIG=kubeconfig
+
+      - name: Deploy to Kubernetes
+        run: |
+          export KUBECONFIG=kubeconfig
+          kubectl set image deployment/api api=${{ vars.PACKAGES_REGISTRY }}/${{ env.IMAGE_NAME }}/api:${{ github.ref_name }} -n datacenter-docs
+          kubectl set image deployment/chat chat=${{ vars.PACKAGES_REGISTRY }}/${{ env.IMAGE_NAME }}/chat:${{ github.ref_name }} -n datacenter-docs
+          kubectl set image deployment/worker worker=${{ vars.PACKAGES_REGISTRY }}/${{ env.IMAGE_NAME }}/worker:${{ github.ref_name }} -n datacenter-docs
+          kubectl rollout status deployment/api -n datacenter-docs --timeout=5m
+          kubectl rollout status deployment/chat -n datacenter-docs --timeout=5m
+          kubectl rollout status deployment/worker -n datacenter-docs --timeout=5m
+
+      - name: Smoke test
+        run: |
+          sleep 30
+          curl -f https://docs.company.local/health || exit 1
+        continue-on-error: true