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>

.yamllint.yml

@@ -0,0 +1,10 @@
+---
+extends: default
+
+rules:
+  line-length:
+    max: 120
+    level: warning
+  document-start: disable
+  truthy:
+    allowed-values: ['true', 'false', 'on', 'off']