Fix shutdown hangs, bank bag icons/drag-drop, loading screen progress, and login spawn

- Fix shutdown hang: skip vmaDestroyAllocator (walked thousands of allocations),
  replace unsafe pthread_timedjoin_np with plain join + early-exit checks in workers
- Bank window: full icon rendering, click-and-hold pickup (0.10s), drag-drop for
  all bank slots including bank bag equip slots, same-slot drop detection
- Loading screen: process one tile per frame for live progress updates
- Camera reset: trust server position in online mode to avoid spawning under WMOs
- Fix PLAYER_BYTES/PLAYER_BYTES_2 field indices, preserve purchasedBankBagSlots
  across inventory rebuilds, fix bank slot purchase result codes

include/rendering/terrain_manager.hpp

@@ -212,6 +212,7 @@ public:
      * Unload all tiles
      */
     void unloadAll();
+    void stopWorkers();  // Stop worker threads without restarting (for shutdown)
     void softReset();  // Clear tile data without stopping worker threads (non-blocking)
 
     /**
@@ -262,6 +263,9 @@ public:
     /** Process all ready tiles immediately (use during loading screens) */
     void processAllReadyTiles();
 
+    /** Process one ready tile (for loading screens with per-tile progress updates) */
+    void processOneReadyTile();
+
 private:
     /**
      * Get tile coordinates from GL world position