game: implement Classic SMSG_FRIEND_LIST and full SMSG_CONTACT_LIST parsing

Classic 1.12 and TBC use SMSG_FRIEND_LIST (not SMSG_CONTACT_LIST) to send
the initial friend list at login. Previously this packet was silently dropped,
leaving friendsCache empty and breaking /friend remove and note operations
for Classic players.

- Add handleFriendList(): parses Classic format (u8 count, then per-entry:
  u64 guid + u8 status + optional area/level/class if online)
- Add handleContactList(): fully parses WotLK SMSG_CONTACT_LIST entries
  (previously only read mask+count header and dropped all entries)
- Both handlers populate friendGuids_ and call queryPlayerName() for unknown
  GUIDs; handleNameQueryResponse() now backfills friendsCache when a name
  resolves for a known friend GUID
- Clear friendGuids_ on disconnect alongside playerNameCache

include/game/game_handler.hpp

@@ -1537,6 +1537,8 @@ private:
     void handleWho(network::Packet& packet);
 
     // ---- Social handlers ----
+    void handleFriendList(network::Packet& packet);   // Classic SMSG_FRIEND_LIST
+    void handleContactList(network::Packet& packet);  // WotLK SMSG_CONTACT_LIST (full parse)
     void handleFriendStatus(network::Packet& packet);
     void handleRandomRoll(network::Packet& packet);
 
@@ -1656,6 +1658,7 @@ private:
 
     // ---- Friend list cache ----
     std::unordered_map<std::string, uint64_t> friendsCache;  // name -> guid
+    std::unordered_set<uint64_t> friendGuids_;               // all known friend GUIDs (for name backfill)
     uint32_t lastContactListMask_ = 0;
     uint32_t lastContactListCount_ = 0;