Add FastAPI interface between the game and map.

A possible explanation for the infrequent CTDs we've been seeing since
adding fast forward is that QWebChannel doesn't keep a reference to the
python objects that it passes to js, so if the object is GC'd before the
front end is done with it, it crashes.

We don't really like QWebChannel anyway, so this begins replacing that
with FastAPI.

game/server/settings.py

@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from functools import lru_cache
+
+from pydantic import BaseSettings
+
+
+class ServerSettings(BaseSettings):
+    """Settings controlling server behavior.
+
+    The values listed here will be automatically modified based on the environment. e.g.
+    running with SERVER_BIND_ADDRESS=0.0.0.0 will cause the server to bind to all
+    interfaces.
+
+    https://fastapi.tiangolo.com/advanced/settings
+    """
+
+    # WARNING: Be extremely cautious exposing the server to other machines. As there is
+    # no client/server workflow yet, security has not been a focus.
+    server_bind_address: str = "::1"
+
+    # If you for some reason change the port, you'll need to also update map.js.
+    server_port: int = 5000
+
+    @classmethod
+    @lru_cache
+    def get(cls) -> ServerSettings:
+        return cls()