feat: display LFG dungeon name in DungeonFinder UI status banner

Extend the LFGDungeons.dbc name lookup to the Dungeon Finder window UI:
- Queued state: "In queue for Culling of Stratholme (1:23)"
- Proposal state: "Group found for Halls of Lightning!"
- InDungeon state: "In dungeon (Utgarde Pinnacle)"
- FinishedDungeon state: "Culling of Stratholme complete"
- Proposal accept banner: "A group has been found for <dungeon>!"
All states fall back gracefully when DBC name is unavailable.

include/game/game_handler.hpp

@@ -1274,6 +1274,7 @@ public:
     bool isLfgQueued()    const { return lfgState_ == LfgState::Queued; }
     bool isLfgInDungeon() const { return lfgState_ == LfgState::InDungeon; }
     uint32_t getLfgDungeonId()   const { return lfgDungeonId_; }
+    std::string getCurrentLfgDungeonName() const { return getLfgDungeonName(lfgDungeonId_); }
     uint32_t getLfgProposalId()  const { return lfgProposalId_; }
     int32_t  getLfgAvgWaitSec()  const { return lfgAvgWaitSec_; }
     uint32_t getLfgTimeInQueueMs() const { return lfgTimeInQueueMs_; }