feat: Add security hardening, agentic coding infrastructure, and test framework

- Add SECRET_KEY and ENCRYPTION_KEY validation on startup
- Implement security headers middleware (X-Frame-Options, CSP, HSTS)
- Add CSRF protection middleware
- Create comprehensive GitHub issue templates and PR template
- Add Makefile with common development tasks
- Configure pre-commit hooks (black, ruff, mypy, bandit, detect-secrets)
- Create docs/CODING_PATTERNS.md with best practices
- Create docs/ERRORS.md documenting all error codes
- Add Architecture Decision Records (ADR) for Celery and Fernet encryption
- Create CHANGELOG.md for version tracking
- Set up pytest test infrastructure with fixtures and factories
- Add sample unit tests for security and config validation
- Create CI/CD workflows (test, lint, security)
- Add comprehensive TODO.md with milestones and progress tracking

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

.github/workflows/lint.yml

@@ -0,0 +1,38 @@
+name: Code Quality
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+    branches: [ main, develop ]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    
+    steps:
+    - uses: actions/checkout@v4
+    
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.11'
+    
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install black ruff mypy
+        pip install -r backend/requirements.txt
+    
+    - name: Check code formatting with Black
+      run: |
+        black --check backend/
+    
+    - name: Lint with Ruff
+      run: |
+        ruff check backend/
+    
+    - name: Type check with mypy
+      run: |
+        mypy backend/app --ignore-missing-imports
+      continue-on-error: true