chore: dockerize api proxy and add gitignore

Add a Docker-based FastAPI proxy skeleton (charter §4) for parity across
dev / homelab VPS / fly.io, plus root .gitignore for Godot 4.7 and Python.

- api/Dockerfile: python:3.12-slim, non-root, PORT-aware CMD
- api/app/main.py: /health + five role endpoint stubs (§4)
- api/requirements.txt: fastapi/uvicorn/httpx/pydantic, pinned
- docker-compose.yml: local dev with live reload
- api/fly.toml: prod deploy stub with /health check
- api/.env.example: key lives in the proxy, never the client (§4)
- .gitignore: ignores .env, whitelists .env.example

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,58 @@
+# ─────────────────────────────────────────────
+# Godot 4.7 (client/)
+# ─────────────────────────────────────────────
+# Editor + import cache (4.x replaced .import/ with .godot/)
+.godot/
+# Exported builds
+/client/build/
+export.cfg
+# export_presets.cfg holds keystore paths / signing config — keep secrets out of history
+export_presets.cfg
+# Mono/C# (only if we drop to C# per charter §16)
+.mono/
+data_*/
+*.mono/
+
+# ─────────────────────────────────────────────
+# Python / FastAPI (api/)
+# ─────────────────────────────────────────────
+__pycache__/
+*.py[cod]
+*$py.class
+*.egg-info/
+.eggs/
+build/
+dist/
+# Virtual envs
+.venv/
+venv/
+env/
+ENV/
+# Tooling caches
+.pytest_cache/
+.mypy_cache/
+.ruff_cache/
+.coverage
+htmlcov/
+.tox/
+
+# ─────────────────────────────────────────────
+# Secrets — the API key lives here in dev, NEVER in the client (charter §4)
+# ─────────────────────────────────────────────
+.env
+.env.*
+!.env.example
+
+# ─────────────────────────────────────────────
+# Editors / OS
+# ─────────────────────────────────────────────
+.vscode/
+.idea/
+*.swp
+.DS_Store
+Thumbs.db
+
+# ─────────────────────────────────────────────
+# Logs (charter §4/§10 logs go to a store, not the repo)
+# ─────────────────────────────────────────────
+*.log