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>

api/fly.toml

@@ -0,0 +1,21 @@
+# fly.io deploy config for the proxy (charter §4, prod). Stub — set app name and
+# region, then `fly deploy` from api/. Secrets (REPLICATE_API_TOKEN) go via
+# `fly secrets set`, never in this file.
+app = "coc-rpg-proxy"      # TODO: claim a real app name
+primary_region = "ord"     # TODO: pick a region
+
+[build]
+  dockerfile = "Dockerfile"
+
+[http_service]
+  internal_port = 8000
+  force_https = true
+  auto_stop_machines = true
+  auto_start_machines = true
+  min_machines_running = 0
+
+[[http_service.checks]]
+  method = "GET"
+  path = "/health"
+  interval = "15s"
+  timeout = "2s"