chore(assets): remove dead icon assets and consolidate icons/

Delete zero-referenced leftovers (31 img SVGs, duplicate top-level
vip badges, favicon/icon/person_background pngs, assets/fonts/,
tmp-debug/, gutenberg-extend.js and the FA eot/ttf/svg font formats)
and give icon-purpose SVGs one home in assets/icons/ (upload-add,
default favicon/logo, playing, user-certification) with every reference
updated. Icon SVG files were audited by name across PHP/CSS/JS before
deletion.

assets/icons/default-favicon.svg

@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32" width="32" height="32">
+  <defs>
+    <linearGradient id="g" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" style="stop-color:#f04494"/>
+      <stop offset="100%" style="stop-color:#ae53f3"/>
+    </linearGradient>
+  </defs>
+  <rect width="32" height="32" rx="6" fill="url(#g)"/>
+  <text x="16" y="22" font-family="system-ui,-apple-system,sans-serif" font-size="18" font-weight="700" fill="#fff" text-anchor="middle">A</text>
+</svg>