feat(command-zone): add server-side support with tests

Implement server-side protocol and game logic for networked command
zone play.

Protocol changes:
- room_commands.proto: command zone messages and responses

Server components:
- ServerCounter: counter synchronization for commander tax
- ServerGame: command zone game state management
- ServerPlayer: player-level command zone handling
- Server/ServerProtocolHandler: command zone message routing
- Servatrice: command zone support in the main server

Design decisions:
- setCount() returns bool for event suppression (avoid duplicate events)
- Zone state synchronized across all connected clients
- Commander tax persists across zone transitions

Test coverage verifies setCount() return value behavior for proper
event suppression in networked scenarios.

libcockatrice_network/libcockatrice/network/server/remote/server.h

@@ -174,6 +174,10 @@ public:
     {
         return false;
     }
+    virtual bool permitCommandZone() const
+    {
+        return true; // Default: allow command zones
+    }
 
     Server_DatabaseInterface *getDatabaseInterface() const;
     int getNextLocalGameId()