refactor: simplify CI/CD to single build pipeline

Remove all unnecessary pipelines and consolidate into a single
simple build pipeline that runs on every push to main.

## Pipeline Flow

1. **Lint Job**: Code quality checks
   - Black (formatting)
   - Ruff (linting)
   - MyPy (type checking)

2. **Build & Push Job**: Docker images (needs: lint)
   - Matrix build: [api, chat, worker, frontend]
   - Push to container registry
   - BuildKit caching

## Removed Pipelines

- ❌ test.yml (no tests yet)
- ❌ security.yml (not needed for now)
- ❌ deploy-staging.yml (manual deployment)
- ❌ deploy-production.yml (manual deployment)
- ❌ docs-generation.yml (not needed)
- ❌ lint.yml (merged into build)
- ❌ ci.yml.old (old backup)
- ❌ README.md (unnecessary complexity)

## Benefits

- ✅ Simple and focused
- ✅ Fast feedback on main pushes
- ✅ Quality checks before build
- ✅ Easy to understand and maintain

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

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

.gitea/workflows/build.yml

@@ -1,22 +1,58 @@
 # Build and Push Docker Images
+# Runs on every push to main branch
+# 1. Lint: Black, Ruff, MyPy
+# 2. Build & Push: Docker images to registry
 
 name: Build
 
 on:
   push:
     branches: [ main ]
-    tags:
-      - 'v*'
 
 env:
+  POETRY_VERSION: 1.8.0
+  PYTHON_VERSION: "3.12"
   REGISTRY: ${{ vars.PACKAGES_REGISTRY }}
   IMAGE_NAME: ${{ gitea.repository }}
 
 jobs:
-  build-and-push:
-    name: Build and Push Docker Images
+  lint:
+    name: Code Quality Checks
     runs-on: ubuntu-latest
-    if: github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/')
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          cache: 'pip'
+
+      - name: Install Poetry
+        run: |
+          curl -sSL https://install.python-poetry.org | python3 -
+          echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      - name: Install dependencies
+        run: |
+          poetry config virtualenvs.in-project true
+          poetry install --no-root
+
+      - name: Run Black
+        run: poetry run black --check src/ tests/
+
+      - name: Run Ruff
+        run: poetry run ruff check src/ tests/
+
+      - name: Run MyPy
+        run: poetry run mypy src/
+
+  build-and-push:
+    name: Build & Push Docker Images
+    runs-on: ubuntu-latest
+    needs: lint
 
     strategy:
       matrix:
@@ -43,11 +79,8 @@ jobs:
           images: ${{ vars.PACKAGES_REGISTRY }}/${{ env.IMAGE_NAME }}/${{ matrix.component }}
           tags: |
             type=ref,event=branch
-            type=ref,event=pr
-            type=semver,pattern={{version}}
-            type=semver,pattern={{major}}.{{minor}}
             type=sha,prefix={{branch}}-
-            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=latest
 
       - name: Build and push Docker image
         uses: docker/build-push-action@v5