Rework the media grid with a viewer, metadata banners, and load gate

docs/media.md

@@ -136,8 +136,14 @@ that deletion is irreversible. The delete button is disabled for a 5 second coun
 - **Media** tab: filter chips (All, Images, GIFs, Videos, Audio), and filters for source (any,
   attachments, stickers, embeds), source channel, poster, aspect ratio (Vertical, 1:1, 4:3, 16:9,
   21:9, Other), resolution (SD, HD, FHD, QHD, 4K+, Unknown), and a posted-date range (from/to).
-  Grid with lazy loading; previews come from the cache, then the local file, then the CDN; each
-  tile's tooltip shows the poster and posted time. A scrape strip shows live progress with Stop.
+  Nothing renders until **Load media** is pressed. A **Metadata** dropdown toggles which fields
+  show in the small banner under each tile (User, Type, Date, Source, Resolution, Length). Video
+  tiles carry a translucent play icon top-right. Clicking a tile opens a viewer: wide media shows
+  the metadata banner below, vertical media shows it to the right; the banner has the full link
+  (with an external-site warning) and **View full**, and the play action embeds a YouTube, Vimeo,
+  Twitch, or Streamable player when possible. The status row reads
+  `downloaded A/B (images/videos) | cached C/D (excludes downloaded) | N loaded`. A scrape strip
+  shows live progress with Stop.
   **New scrape…** (rightmost) opens a popup with Server and Group chat trees (servers expand to
   channels; each row has Links and Download). Every scrape button asks for confirmation; the
   dialog takes optional From/To dates and a **Check Message Count** button (Discord search total,