feat(gems): add multiplayer gem game with custom content packs

- implement FastAPI and HTMX lobby and game interfaces
- support up to four human and AI-controlled players
- add configurable rules, victory conditions, and expansion modules
- support validated JSON cards, patrons, objectives, and outposts

python/gems/config.py

@@ -0,0 +1,25 @@
+"""Runtime configuration loaded from environment variables."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class GemsConfig(BaseSettings):
+    """Configure persistence, public URLs, cookies, and the HTTP server."""
+
+    model_config = SettingsConfigDict(env_prefix="GEMS_")
+
+    database_path: Path = Path(".gems/gems.sqlite3")
+    key_path: Path = Path(".gems/instance.key")
+    public_origin: str = "http://127.0.0.1:8082"
+    secure_cookies: bool = False
+    host: str = "127.0.0.1"
+    port: int = 8082
+
+
+def load_config() -> GemsConfig:
+    """Load Gems configuration from defaults and environment variables."""
+    return GemsConfig()