Buddy code cleanup

- Get rid of buddyCnt, self-nullptr checks, and redundant playermap loops in chat handlers
- Add helper function to find available buddy slot
- Reorganize a bit

src/main.cpp

@@ -99,7 +99,7 @@ int main() {
     NanoManager::init();
     NPCManager::init();
     TransportManager::init();
-    BuddyManager::init(); // stubbed until we have database integration + lots of bug fixes
+    BuddyManager::init();
     GroupManager::init();
     Database::open();