feat(games): unify ApplyMove signatures + remove unused player conversion

Updated TicTacToeRules and BattleshipRules to implement ApplyMove(state, playerIdx, payload) (bool, bool, int) as required by GameRules.

Added win/draw resolution logic directly inside each game’s ApplyMove return.

Removed obsolete convertToGamePlayers helper.

Updated GenericMatch to call AssignPlayerSymbols with []*structs.Player directly.

Ensured all rule implementations now fully satisfy the GameRules interface.

plugins/games/rules.go

@@ -12,7 +12,7 @@ type GameRules interface {
     MaxPlayers() int
 
     // Assign symbols/colors/pieces at start.
-    AssignPlayerSymbols(players []*Player)
+    AssignPlayerSymbols(players []*structs.Player)
 
     // Apply a move.
     // Returns: (changed, gameOver, winnerIndex)