feat: enhance Zuma menu with background image and improve UI layout

- Add background image to Zuma title screen with solid color fallback
- Add new depth layer for background rendering (D.bg)
- Style progress text with semi-transparent background rectangle
- Reposition game buttons grid lower on screen for better visual balance
- Register zuma-menu-bg asset in manifest for lazy loading
- Add Advance Wars and Zuma image assets (background, frog sprite)

src/data/assetManifest.js

@@ -313,6 +313,9 @@ export const MANIFEST = {
     // its audio only downloads once Dot Link is actually entered.
     (scene) => musicFrom(scene, 'hacker-music'),
   ],
+  zuma: [
+    image('zuma-menu-bg', 'assets/images/zuma/background-menu.png'),
+  ],
   '2048': [
     // hacker soundtrack (see services/soundtrack.js) — lazy-loaded here so
     // its audio only downloads once 2048 is actually entered.

src/games/zuma/ZumaGame.js

@@ -11,7 +11,7 @@ import {
 const BG       = 0x0d1a10;          // deep jungle green
 const PATH_RIM = 0x241b0e;
 const PATH_BED = 0x4a3a26;
-const D = { path: 0, hole: 2, ball: 10, icon: 11, flight: 12, laser: 13, frog: 14, fx: 20, ui: 30, overlay: 60, overlayUI: 62 };
+const D = { path: 0, hole: 2, ball: 10, icon: 11, flight: 12, laser: 13, frog: 14, fx: 20, ui: 30, bg: -2, overlay: 60, overlayUI: 62 };
 
 // glossy marble palette: red, yellow, blue, green, purple, silver
 const BALL_COLORS = [0xd9403a, 0xeec23d, 0x3f7fdb, 0x43b059, 0x9b59d0, 0xd9dde3];
@@ -202,15 +202,16 @@ export default class ZumaGame extends Phaser.Scene {
     this.overlayUp = false;
     this.state = null;
     this.clearLayer();
-    const cx = GAME_WIDTH / 2;
 
-    const title = this.add.text(cx, 84, 'ZUMA', {
-      fontFamily: 'Righteous', fontSize: '72px', color: COLORS.goldHex,
-    }).setOrigin(0.5);
-    const sub = this.add.text(cx, 148, 'Shoot marbles into the rolling chain — match 3+ to pop them all before the skull feeds. Right-click or SPACE swaps.', {
-      fontFamily: '"Julius Sans One"', fontSize: '22px', color: COLORS.mutedHex,
-    }).setOrigin(0.5);
-    this.layer.add([title, sub]);
+    // Background image (falls back to solid color if not loaded)
+    if (this.textures.exists('zuma-menu-bg')) {
+      this.layer.add(this.add.image(GAME_WIDTH / 2, GAME_HEIGHT / 2, 'zuma-menu-bg')
+        .setDisplaySize(GAME_WIDTH, GAME_HEIGHT).setDepth(D.bg));
+    } else {
+      this.layer.add(this.add.rectangle(GAME_WIDTH / 2, GAME_HEIGHT / 2, GAME_WIDTH, GAME_HEIGHT, BG).setDepth(D.bg));
+    }
+
+    const cx = GAME_WIDTH / 2;
 
     if (!this.bank.length) {
       const msg = this.add.text(cx, 520, 'No levels found.\nRun: node server/scripts/genZuma.js', {
@@ -223,17 +224,20 @@ export default class ZumaGame extends Phaser.Scene {
     }
 
     const nextLevel = Math.min(this.levelsCompleted + 1, this.bank.length);
-    const prog = this.add.text(cx, 192, `Completed ${this.levelsCompleted} / ${this.bank.length}`, {
+    const bg = this.add.rectangle(cx, 442, 320, 56, 0x000000, 0.55)
+      .setStrokeStyle(2, 0x6b5638, 0.8)
+      .setOrigin(0.5);
+    const prog = this.add.text(cx, 442, `Completed ${this.levelsCompleted} / ${this.bank.length}`, {
       fontFamily: 'Righteous', fontSize: '24px', color: COLORS.textHex,
     }).setOrigin(0.5);
-    this.layer.add(prog);
+    this.layer.add([bg, prog]);
 
     const COLS = 10;
     const SIZE = 120;
     const GAP = 16;
     const gridW = COLS * SIZE + (COLS - 1) * GAP;
     const left = cx - gridW / 2 + SIZE / 2;
-    const top = 300;
+    const top = 550;
 
     this.bank.forEach((l, i) => {
       const col = i % COLS;