refactor(matchmaking): migrate Python simulator to native Nakama matchmaker

### Summary
Replaced legacy RPC-based matchmaking flow with proper WebSocket-driven
matchmaker integration. Player simulation now queues via
`matchmaker_add`, auto-joins matches on `matchmaker_matched`, and no
longer depends on `rpc_find_match`.

game_flow.py

@@ -118,17 +118,27 @@ class PlayerWebSocketHandler(WebSocketHandler):
             print(f"[{self.label}] UNKNOWN OPCODE {op}: {payload}")
 
     # ---------- Match Helpers ----------
-    def rpc_find_match(self) -> str:
-        """Call rpc_find_match and return Nakama match_id."""
-        r = requests.post(
-            f"{HOST}/v2/rpc/rpc_find_match",
-            headers={"Authorization": f"Bearer {self.token}"},
-        )
-        r.raise_for_status()
+    async def join_matchmaking(self, mode: str = "classic"):
+        """Queue into Nakama matchmaker."""
+        await self.ws.send(json.dumps({
+            "matchmaker_add": {
+                "min_count": 2,
+                "max_count": 2,
+                "string_properties": {
+                    "mode": mode
+                }
+            }
+        }))
+        print(f"[{self.label}] Searching match for mode={mode}...")
 
-        # RPC returns {"payload": "<json string>"}
-        payload = json.loads(r.json()["payload"])
-        return payload["match_id"]
+    async def leave_matchmaking(self, ticket: str):
+        """Remove player from Nakama matchmaking queue."""
+        await self.ws.send(json.dumps({
+            "matchmaker_remove": {
+                "ticket": ticket
+            }
+        }))
+        print(f"[{self.label}] Left matchmaking queue")
 
     async def create_match(self) -> str:
         await self.ws.send(json.dumps({"match_create": {}}))