feat: new TwoPointZero branding - icons, favicon, mockup i18n

- Replace extension icons with new TwoPointZero design (16/32/48/96/128)
- Update manifest.base.json with 32+96 icon sizes
- Increase popup logo to 48px, website nav logo to 64px
- Generate website webp sizes (64/128/200) + AVIF variants from 600px source
- Add favicon PNGs (16x16, 32x32) + apple-touch-icon + 192x192
- Fix logo vertical centering via display:contents on picture wrappers
- Convert mockup section from inline <span lang> pairs to {{MOCK_*}} template vars
- Add MOCK translations for FR, ES, PT-BR, RU locale files
- Bump AVIF quality 70->80, speed 6->4, remove min 3KB threshold
- Regenerate www/ with build.js

website/join.html

@@ -6,7 +6,9 @@
     <title>Join Room | KoalaSync</title>
     <link rel="preload" href="style.min.css" as="style">
     <link rel="stylesheet" href="style.min.css">
-    <link rel="icon" type="image/webp" href="assets/NewLogoIcon_64.webp">
+    <link rel="icon" type="image/png" sizes="16x16" href="assets/favicon-16x16.png">
+    <link rel="icon" type="image/png" sizes="32x32" href="assets/favicon-32x32.png">
+    <link rel="apple-touch-icon" sizes="180x180" href="assets/icon-192x192.png">
     <meta name="robots" content="noindex">
 
     <!-- Open Graph / Facebook -->
@@ -39,7 +41,7 @@
     <nav>
         <div class="container nav-content">
             <a href="./" class="logo-area" style="text-decoration: none;">
-                <img src="assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="40" height="40">
+                <img src="assets/NewLogoIcon.webp" alt="KoalaSync Logo" width="64" height="64">
                 <span>KoalaSync</span>
             </a>
             <button class="hamburger" aria-label="Menu" aria-expanded="false">☰</button>