feat: complete YouTube-style site experience for YMB

- rebuild home feed with sticky server-driven categories and skeletons
- add full-screen shorts feed with likes, comments, saves and follows
- rebuild watch page with same-drama episode swiping and locked states
- wire search, watch history and episode stats to the app API
- add about page with app store links and an upload video dialog
- add SVG language flags, formatted view counts and site icons

index.html

@@ -5,6 +5,9 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="theme-color" content="#0f0f0f" />
+    <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png" />
+    <link rel="icon" type="image/png" sizes="192x192" href="/favicon-192x192.png" />
+    <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png" />
     <meta name="description" content="YMB — short stories, big emotions." />
     <meta name="robots" content="index,follow,max-image-preview:large" />
     <link rel="canonical" href="https://ymb.example.com/" />