fix(subs): stop the lock/reload on source actions + regroup the row buttons

Lock/reload: every inline source action (check / backfill / recover / toggle /
remove) ended by refetching the WHOLE subscription list (store.loadAll /
refresh), which blocked the UI and re-rendered the table — collapsing the
expanded row, which read as "locks then resets." The action APIs already return
the updated source, so the store now patches that one row in place
(_patchSource / _dropSource); the post-action loadAll/refresh calls are gone.
Toggling enabled, starting/stopping a backfill, recovering, and removing are now
instant and leave the expansion intact.

Button regroup (operator-flagged: tiny, mis-clickable, not grouped by function):
- New shared SourceActions.vue used by desktop SourceRow + mobile SourceCard.
- Frequent actions stay as size="small" buttons: Check, Backfill/Stop.
- Low-frequency / destructive actions move into a labelled overflow (⋮) menu —
  Preview backfill, Recover dropped near-duplicates, Remove source — so they
  can't be fat-fingered, and the labels spell out recover-vs-backfill.
- Edit moves next to the source URL (its identity), out of the action cluster
  where it sat beside Remove.
- Single-source Remove now confirms (it had no guard before).

Tests: store patches/drops in place without dropping the cache.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/subscriptions/SubscriptionsTab.vue

@@ -491,13 +491,26 @@ function openEditSource(source) {
 }
 
 async function removeSource(source) {
-  await store.remove(source.id, source.artist_id)
-  await refresh()
+  // Confirm — Remove moved into the overflow menu, but a destructive action
+  // still deserves a guard (single-source removal had none before).
+  if (!globalThis.window?.confirm(
+    `Remove this ${source.platform} source?\n${source.url}\n\nThe artist and already-downloaded images stay.`,
+  )) return
+  try {
+    // store._dropSource patches the cache in place — no full reload, so the
+    // table + expansion don't reset (operator-flagged lock/reload, 2026-06-07).
+    await store.remove(source.id, source.artist_id)
+  } catch (e) {
+    toast({ text: `Remove failed: ${e?.body?.detail || e?.message || e}`, type: 'error' })
+  }
 }
 
 async function toggleSourceEnabled({ source, enabled }) {
-  await store.update(source.id, { enabled }, source.artist_id)
-  await refresh()
+  try {
+    await store.update(source.id, { enabled }, source.artist_id)
+  } catch (e) {
+    toast({ text: `Update failed: ${e?.body?.detail || e?.message || e}`, type: 'error' })
+  }
 }
 
 async function onSourceSaved() {
@@ -557,7 +570,7 @@ async function onBackfill(source) {
       await store.startBackfill(source.id, source.artist_id)
       toast({ text: `Backfill started for ${source.artist_name}`, type: 'success' })
     }
-    await store.loadAll()
+    // startBackfill/stopBackfill patch the source in place — no full reload.
   } catch (e) {
     toast({
       text: `Backfill ${running ? 'stop' : 'start'} failed: ${e?.body?.detail || e?.message || e}`,
@@ -573,7 +586,7 @@ async function onRecover(source) {
   try {
     await store.recoverSource(source.id, source.artist_id)
     toast({ text: `Recovery started for ${source.artist_name}`, type: 'success' })
-    await store.loadAll()
+    // recoverSource patches the source in place — no full reload.
   } catch (e) {
     toast({
       text: `Recovery start failed: ${e?.body?.detail || e?.message || e}`,