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/server.py

@@ -0,0 +1,35 @@
+import time
+from collections.abc import Iterator
+from contextlib import contextmanager
+from threading import Thread
+
+import uvicorn
+from uvicorn import Config
+
+from game.server.settings import ServerSettings
+
+
+class Server(uvicorn.Server):
+    def __init__(self) -> None:
+        super().__init__(
+            Config(
+                "game.server.app:app",
+                host=ServerSettings.get().server_bind_address,
+                port=ServerSettings.get().server_port,
+                log_level="info",
+            )
+        )
+
+    @contextmanager
+    def run_in_thread(self) -> Iterator[None]:
+        # This relies on undocumented behavior, but it is what the developer recommends:
+        # https://github.com/encode/uvicorn/issues/742
+        thread = Thread(target=self.run)
+        thread.start()
+        try:
+            while not self.started:
+                time.sleep(1e-3)
+            yield
+        finally:
+            self.should_exit = True
+            thread.join()