v3: generated placeholder thumbnails for pages with no preview image, and a fix for hotlink-protected ones

Thumbnails were failing in two different ways that both ended as an empty box.

Cloudflare hotlink protection answers a cross-site Referer with 403, so images
we had extracted correctly (dles.aukspot.com's og:image among them) never
rendered — every onError handler set display:none and swallowed it. The new
Thumbnail component loads with referrerPolicy="no-referrer", retries once
through /api/proxy-image for hosts that reject an empty referrer too, and only
then falls back to a placeholder.

Separately, the extraction cascade ended at the page's icon and then a guessed
/favicon.ico, so thumbnailUrl was almost never empty — just a 16x16 icon
cover-cropped into a 128x72 box. It now stops at real artwork, with faviconUrl
and accentColor (theme-color / msapplication-TileColor / mask-icon) as their own
fields. An absent thumbnailUrl finally means "no artwork", which is what makes
the placeholder possible: the site's own color mixed into the theme surface,
with its favicon centered on it, or its initial. Contrast holds for any
third-party color by construction rather than by luminance math, so nyt only
has to set --thumb-tint-strength to 0% to stay monochrome and geocities only
has to raise it. Missing accents fall back to a stable hostname-derived hue, so
rows saved before this get a tint with no backfill.

Migration 0011 reclassifies favicon-shaped thumbnailUrls on existing dumps.
The journal mosaic keeps its pull-quote and text fallbacks — the placeholder
appears there only to repair a broken image.

Also fixed: refresh silently overwrote good metadata with a failure stub, the
refresh button swallowed every error, refresh never broadcast the update,
extractBestIcon ranked SVG icons below 16x16 PNGs, and shared links with no
artwork carried no og:image at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

api/db/migrate.ts

@@ -9,6 +9,7 @@ import { up as up0007PasswordResetTokens } from "./migrations/0007_password_rese
 import { up as up0008ChatMessages } from "./migrations/0008_chat_messages.ts";
 import { up as up0009ChatReply } from "./migrations/0009_chat_reply.ts";
 import { up as up0010YoutubeEmbedStart } from "./migrations/0010_youtube_embed_start.ts";
+import { up as up0011SplitFaviconThumbnail } from "./migrations/0011_split_favicon_thumbnail.ts";
 
 interface Migration {
   name: string;
@@ -29,6 +30,7 @@ const MIGRATIONS: Migration[] = [
   { name: "0008_chat_messages", up: up0008ChatMessages },
   { name: "0009_chat_reply", up: up0009ChatReply },
   { name: "0010_youtube_embed_start", up: up0010YoutubeEmbedStart },
+  { name: "0011_split_favicon_thumbnail", up: up0011SplitFaviconThumbnail },
 ];
 
 export function runMigrations(db: DatabaseSync): void {