Menu screens: rock background, centred frame, logo, 3D hero

- Spielen hero panel shows the selected hero in 3D (cUI_NetGranny,
  game/ui/granny.h).
- All menu screens draw on the options' rock wall; the main menu's 1024
  frame is drawn centred over it, mouse and cursor shifted to match.
- The main menu's and options' own pictures and the main menu's 3D scene
  are left out (textures hidden by surface, scene call redirected).
- Logo top left: FX_SACREDLOGO.TGA, drawn added.
- Game textures by name (game/ui/texture.h), textured and added quads.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/widescreen.md

@@ -67,9 +67,11 @@ Elsewhere (unknown / UI, leave alone for now): `0x40694a`, `0x4ec036`,
 | `0x006469d0` | loading screen: GDI BitBlt of bitmap + progress bar + text into the back buffer (fixed 1024x768) | render thread |
 | `0x006a0c60` | video/intro playback (unexamined) | |
 
-The widescreen mod gives these frames a 1024x768 D3D viewport (set at
+The widescreen mod gives the loading screen a 1024x768 D3D viewport (set at
 `BeginScene` when the scene depth `+0x1d8` is 0) and the borderless mod
-presents only that area, scaled to the monitor.
+presents only that area, scaled to the monitor. The main menu thread renders
+the full width since 2026-10-20: its 1024x768 frame is drawn centred on the
+menu screens' background (docs/screens.md, "Main menu frame").
 
 ## Direct3D 7 render target limit