refactor(game): add Map.closest and improve flag assignment logic

- Introduced `Map.closest` to encapsulate nearest‑position search and replaced duplicated distance loops in flag targeting.
- Updated flag assignment to consider enemy players carrying flags and to use the new helper for both ally and enemy flag selection.
- Cleaned up unused imports and renamed `mypolicy` to `mypolicy.py` for clarity.
- Adjusted frontend `game_config.json` to use new team identifiers, increase players to 3, raise flag count to 9, and enable random flag placement.

CTF/frontend/game_config.json

@@ -1,16 +1,16 @@
 {
   "teams": [
-    { "name": "L", "who": "user11-1"},
-    { "name": "R", "who": "human"}
+    { "name": "L", "who": "user0-1"},
+    { "name": "R", "who": "user0-2"}
   ],
   "setup": {
-    "numPlayers": 1,
-    "numFlags": 3,
-    "useRandomFlags": false
+    "numPlayers": 3,
+    "numFlags": 9,
+    "useRandomFlags": true
   },
   "servers": {
-    "user0-1": "ws://115.191.4.103:34568",
-    "user0-2": "ws://115.191.4.103:34569",
+    "user0-1": "ws://0.0.0.0:11451",
+    "user0-2": "ws://0.0.0.0:11452",
     "user1-1": "ws://115.191.4.103:34571",
     "user1-2": "ws://115.191.4.103:34572",
     "user2-1": "ws://115.191.4.103:34574",