feat: initial project setup

- FastAPI backend (Python 3.12, uv)
- React 19 + TypeScript + Vite frontend
- Devcontainer with Node 22, Python 3.12, uv, opencode
- Basic app structure and project docs

.gitignore

@@ -0,0 +1,27 @@
+# Python
+__pycache__/
+*.py[cod]
+*.egg-info/
+.venv/
+*.egg
+
+# Node
+node_modules/
+dist/
+
+# Environment
+.env
+.env.local
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# uv
+uv.lock