Fix PWA install: static manifest.json + proper SVG icon

- Replace blob: manifest (ignored by Chrome) with static manifest.json
- Replace data: URL icon with real icon.svg file
- Link manifest and apple-touch-icon directly in <head>
- Remove blob/data URL generation from app.js

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

icon.svg

@@ -0,0 +1,22 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
+  <rect width="512" height="512" rx="90" fill="#07070f"/>
+  <rect width="512" height="512" rx="90" fill="url(#bg)"/>
+  <defs>
+    <radialGradient id="bg" cx="30%" cy="40%" r="80%">
+      <stop offset="0%" stop-color="#1a1a2e"/>
+      <stop offset="100%" stop-color="#07070f"/>
+    </radialGradient>
+  </defs>
+  <!-- Music note -->
+  <g fill="#e8a020">
+    <!-- Note head 1 -->
+    <ellipse cx="180" cy="340" rx="48" ry="36" transform="rotate(-15 180 340)"/>
+    <!-- Note head 2 -->
+    <ellipse cx="332" cy="300" rx="48" ry="36" transform="rotate(-15 332 300)"/>
+    <!-- Stem -->
+    <rect x="218" y="160" width="18" height="185" rx="9"/>
+    <rect x="370" y="120" width="18" height="185" rx="9"/>
+    <!-- Beam -->
+    <rect x="218" y="160" width="170" height="22" rx="11"/>
+  </g>
+</svg>