feat(header): clarify video counts and hide idle pause button

Show 'N yours / M total' in the header (your subscriptions vs. the whole shared
catalog) with a tooltip, backed by a new total_videos field on /sync/my-status.
The admin pause button now only appears when there's sync work to pause; Resume
still shows whenever sync is paused.

backend/app/routes/sync.py

@@ -152,6 +152,9 @@ def my_status(
             ),
         )
     )
+    # Whole-catalog total (every video any user's subscriptions have pulled in), so the
+    # header can show "yours" against the shared library size.
+    total_videos = db.scalar(select(func.count(Video.id)))
     return {
         "channels_total": total,
         "channels_details_synced": details_synced,
@@ -163,6 +166,7 @@ def my_status(
         "deep_pending_count": deep_eta["channels_pending"],
         "deep_eta_seconds": deep_eta["eta_seconds"],
         "my_videos": my_videos or 0,
+        "total_videos": total_videos or 0,
         "quota_used_today": quota.units_used_today(db),
         "quota_remaining_today": quota.remaining_today(db),
         "paused": state.is_sync_paused(db),

frontend/src/components/SyncStatus.tsx

@@ -34,8 +34,16 @@ export default function SyncStatus({
 
   return (
     <div className="hidden lg:flex items-center gap-2 text-xs text-muted">
+      <Tooltip hint="Videos from your subscriptions, against the total in the shared catalog that every user's subscriptions have pulled in.">
+        <span className="flex items-center gap-1.5 cursor-default">
           <Database className="w-3.5 h-3.5" />
-      <span>{formatViews(data.my_videos)} videos</span>
+          <span>
+            <span className="text-fg font-medium">{formatViews(data.my_videos)}</span> yours
+          </span>
+          <span className="opacity-40">/</span>
+          <span>{formatViews(data.total_videos)} total</span>
+        </span>
+      </Tooltip>
       <span className="opacity-40">·</span>
       {data.paused ? (
         <span className="text-accent font-medium">paused</span>
@@ -61,7 +69,9 @@ export default function SyncStatus({
           </Tooltip>
         </>
       )}
-      {isAdmin && (
+      {/* Pause only makes sense when there's work to pause; Resume must always show
+          while paused so it can be lifted. Hidden entirely when idle and not paused. */}
+      {isAdmin && (data.paused || syncing > 0) && (
         <button
           onClick={() => toggle.mutate()}
           disabled={toggle.isPending}

frontend/src/lib/api.ts

@@ -173,6 +173,7 @@ export interface MyStatus {
   deep_pending_count: number;
   deep_eta_seconds: number;
   my_videos: number;
+  total_videos: number;
   quota_used_today: number;
   quota_remaining_today: number;
   paused: boolean;