feat(FN-003): add tool manifest registry with FastAPI CRUD and built-in manifests

- Add ToolManifest Pydantic models with validators for ports, mounts, health checks, and traefik config

- Implement in-memory ToolRegistry with YAML loading and built-in manifest scanning

- Add FastAPI CRUD routes for listing, retrieving, and creating tool manifests

- Include built-in manifests for runfusion and code-server

- Harden web Dockerfile with unprivileged nginx and port 8080

- Add tool manifest specification documentation and architecture updates

Fusion-Task-Id: FN-003

.env.example

@@ -6,6 +6,7 @@ TOOL_DOMAIN=tools.localhost
 # API / Web URLs
 API_URL=http://localhost:8000
 WEB_URL=http://localhost:5173
+CORS_ORIGINS=http://localhost:5173
 
 # Database (local development)
 POSTGRES_USER=postgres