feat: add Django project scaffold, configuration and container

Environment-variable configuration that fails fast, database-only health
check, JSON request logs with a request id, security headers with a strict
CSP, and a multi-stage non-root Docker image with compose file. Ticket 1.1.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sk72AxLwQnYttF6VFSxQLt

.gitignore

@@ -22,3 +22,16 @@
 
 # BMAD generated render cache
 _bmad/render/
+
+# Python / project
+.venv/
+__pycache__/
+*.pyc
+.pytest_cache/
+.ruff_cache/
+staticfiles/
+*.sqlite3
+*.sqlite3-*
+.env
+.env.*
+!.env.example