feat(editor): zone metadata panel with mapId, displayName, gameplay flags

- Map ID: configurable integer input (0-65535) for private server
  integration. Custom zones default to 9000+ to avoid Blizzard conflicts
- Display Name: editable text field for in-game world map/loading screen
- Description: multi-line text field for zone documentation
- Zone Flags: Allow Flying, PvP Enabled, Indoor, Sanctuary checkboxes
- All fields serialized to zone.json under "flags" key
- Info panel shows quest count alongside objects/NPCs

tools/editor/zone_manifest.hpp

@@ -17,6 +17,12 @@ struct ZoneManifest {
     bool hasCreatures = false;
     std::string description;
 
+    // Zone gameplay flags
+    bool allowFlying = false;
+    bool pvpEnabled = false;
+    bool isIndoor = false;
+    bool isSanctuary = false;
+
     // Audio configuration
     std::string musicTrack;         // Background music file path
     std::string ambienceDay;        // Daytime ambient sound