feat: desert dusk theme with animated mule and pixel-art scenery

Replaces the cool-grey neutral theme with a warm desert dusk palette
pulled from a new pixel-art TopBar: a tiled, right-to-left scrolling
desert under a sky gradient, a 6-frame walking mule sprite where the
logo used to sit, and an ASCII block-character title on a black plate.
The active heap card now uses a cactus/dune scene as its stack
backdrop, and the "Built with hubris" mark moves into the TopBar's
bottom-right corner (AppFooter component removed).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/tailwind.config.js

@@ -8,19 +8,22 @@ export default {
   theme: {
     extend: {
       colors: {
-        // Dark-first color scheme for photo apps
-        bg: '#111110',
-        surface: '#161615',
-        'surface-2': '#1c1c1a',
-        'surface-offset': '#222220',
-        border: 'rgba(255,255,255,0.08)',
-        text: '#e8e6e0',
-        'text-muted': '#878580',
-        'text-faint': '#4a4845',
-        primary: '#3b82f6', // saturated blue (Tailwind blue-500) — high contrast on dark bg AND on photo content
-        pick: '#4f9e5c',    // green for picked
-        reject: '#c25a5a',  // red for rejected
-        star: '#d4a340',    // amber for stars
+        // Desert dusk palette — warm, slightly indigo darks pulled from
+        // the TopBar sunset gradient. Dark enough that photo content
+        // stays the visual focus, but no longer the cool neutral greys
+        // we started with.
+        bg: '#1a1424',           // deep dusk indigo (was near-black)
+        surface: '#221c2f',       // panel base
+        'surface-2': '#2a2339',   // raised panels / hover
+        'surface-offset': '#352c46', // chips, inputs
+        border: 'rgba(240, 193, 136, 0.10)', // warm sand tint, low alpha
+        text: '#f0e6d2',          // warm cream
+        'text-muted': '#a8997d',  // sandy beige
+        'text-faint': '#5e5448',  // dark sand
+        primary: '#e8965a',       // sunset orange — pulled from horizon
+        pick: '#8aaa5a',          // sage / cactus green
+        reject: '#d06464',        // warmer red
+        star: '#f0c188',          // pale amber matching horizon
       },
       fontFamily: {
         sans: ['Geist', 'system-ui', 'sans-serif'],