chore: release version 2.3.5 and refactor lobby

Bump export_presets.cfg version to 2.3.5. Update CHANGELOG_DRAFT.md.
Refactor lobby.gd into LobbyChat, LobbyMainMenu, LobbyRoomList, LobbyRoom.
Move Nakama config to environment variables in nakama_manager.gd.
Derive auth_manager.gd encryption key from OS.get_unique_id().sha256_text().
Remove Steam email auth fallback. Require auth ticket.
Make GachaManager.pull() async in gacha_panel.gd.
Remove dummy wallet seeding. Add store_type to IAP payload.
Validate IAP receipts server-side in economy.lua.
Register gacha module in main.lua.
Clean backend_service.gd stubs.
Fix featured_banners type safety in gacha_manager.gd. Guards non-array responses.
Move tiles_armagedon_a1.res to assets/models/meshes/. Fix import fallback_path.

assets/models/meshes/tiles_armagedon.glb.import

@@ -76,7 +76,7 @@ _subresources={
 "lods/normal_merge_angle": 60.0,
 "lods/normal_split_angle": 25.0,
 "save_to_file/enabled": true,
-"save_to_file/fallback_path": "res://tiles_armagedon_a1.res",
+"save_to_file/fallback_path": "res://assets/models/meshes/tiles_armagedon_a1.res",
 "save_to_file/path": "uid://dc8xogqvnqor7"
 },
 "tiles_armagedon_Cube_012": {