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.

addons/gut/gui/gut_dock.gd

@@ -0,0 +1,37 @@
+extends EditorDock
+
+
+var _panel : Control = null
+var _current_layout = -1
+
+
+func _update_layout(layout):
+	_current_layout = layout
+	if(_panel != null):
+		if(layout == DOCK_LAYOUT_FLOATING):
+			_windowed_mode()
+		else:
+			_dock_mode()
+
+
+# -------------
+# Private
+# -------------
+func _windowed_mode():
+	_panel.show_layout_buttons(true)
+
+
+func _dock_mode():
+	_panel.results_horiz_layout()
+	_panel.show_layout_buttons(false)
+
+
+# -------------
+# Public
+# -------------
+func add_bottom_panel(gut_bottom_panel):
+	_panel = gut_bottom_panel
+	# Make floating button not supported right now
+	add_child(_panel)
+	_panel.make_floating_btn.visible = false
+	_update_layout(_current_layout)