fix(activity): filter empty categories from activity feed tabs (#152)

* fix(activity): filter empty categories from activity feed tabs

Only include categories in availableCategories when the user has apps
with recentCount > 0. Previously, the scanner created rows for all
registered apps (including those with zero records), causing empty
category tabs like "Photos" to appear with no content.

* fix(activity): pass resolved Bluesky embeds with thumb URLs

The Bluesky AppView API returns resolved embeds (with CDN thumb URLs)
on item.post.embed, but we were only passing item.post.record which
has raw blob refs. Merge the resolved embed into the record so the
frontend card can display image thumbnails and link preview images.

src/routes/activity.ts

···
 }
 
 /**
+ * Merge resolved embed (with thumb URLs) from the Bluesky AppView into
+ * the raw record. The raw record only has blob refs for images; the
+ * AppView response includes resolved CDN URLs in item.post.embed.
+ */
+function mergeResolvedEmbed(record: unknown, embed: unknown): unknown {
+  if (!embed || typeof record !== 'object' || record === null) return record;
+  return { ...(record as Record<string, unknown>), embed };
+}
+
+/**
  * Fetch recent items from Bluesky via the public AppView API.
  */
 async function fetchBlueskyItems(did: string, limit: number): Promise<ActivityItem[]> {
···
       uri: item.post.uri,
       collection: 'app.bsky.feed.post',
       rkey: extractRkey(item.post.uri),
-      record: item.post.record,
+      record: mergeResolvedEmbed(item.post.record, item.post.embed),
       appId: 'bluesky',
       appName: 'Bluesky',
       category: 'Posts',
···
       uri: item.post.uri,
       collection: 'app.bsky.feed.post',
       rkey: extractRkey(item.post.uri),
-      record: item.post.record,
+      record: mergeResolvedEmbed(item.post.record, item.post.embed),
       appId: 'bluesky',
       appName: 'Bluesky',
       category: 'Posts',
···
     const stats = await getVisibleAppStats(db, did);
     const registry = getAppsRegistry();
 
-    // Compute available categories from all visible apps the user has
-    // (a row exists in user_app_stats when the scanner found the collection in the PDS)
+    // Compute available categories from apps that actually have recent content
     const availableCategories = [
       ...new Set(
         stats
+          .filter((s) => s.recentCount > 0)
           .map((s) => registry.find((e) => e.id === s.appId)?.category)
           .filter((c): c is string => c !== undefined),
       ),
     ];
-    // Filter apps by category if specified
+    // Filter apps by category if specified, skipping apps with no recent content
+    const activeStats = stats.filter((s) => s.recentCount > 0);
     let targetApps: { stat: (typeof stats)[number]; entry: AppRegistryEntry }[];
     if (categoryParam === 'all') {
-      targetApps = stats
+      targetApps = activeStats
         .slice(0, 5)
         .map((stat) => {
           const entry = registry.find((e) => e.id === stat.appId);
···
         })
         .filter((x): x is NonNullable<typeof x> => x !== null);
     } else {
-      targetApps = stats
+      targetApps = activeStats
         .map((stat) => {
           const entry = registry.find((e) => e.id === stat.appId);
           return entry && entry.category === categoryParam ? { stat, entry } : null;