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/images/VSplitContainer.svg

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   width="16"
+   height="16"
+   version="1.1"
+   id="svg4"
+   sodipodi:docname="VSplitContainer.svg"
+   inkscape:version="1.2.2 (b0a84865, 2022-12-01)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <defs
+     id="defs8" />
+  <sodipodi:namedview
+     id="namedview6"
+     pagecolor="#505050"
+     bordercolor="#eeeeee"
+     borderopacity="1"
+     inkscape:showpageshadow="0"
+     inkscape:pageopacity="0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#505050"
+     showgrid="false"
+     inkscape:zoom="14.75"
+     inkscape:cx="7.8305085"
+     inkscape:cy="8"
+     inkscape:window-width="1512"
+     inkscape:window-height="864"
+     inkscape:window-x="202"
+     inkscape:window-y="1118"
+     inkscape:window-maximized="0"
+     inkscape:current-layer="svg4" />
+  <path
+     fill="#8eef97"
+     d="M15 3a2 2 0 0 0-2-2H3a2 2 0 0 0-2 2v10a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2zm-2 0v4h-3L8 5 6 7H3V3zm0 6v4H3V9h3l2 2 2-2z"
+     id="path2"
+     style="fill-opacity:1.0;fill:#ffffff" />
+</svg>