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/SourceActions.vue

@@ -0,0 +1,91 @@
+<template>
+  <!-- Shared per-source action cluster (desktop SourceRow + mobile SourceCard).
+       Frequent actions stay as buttons; low-frequency / destructive ones move
+       into a labelled overflow menu so they can't be mis-clicked, and the
+       labels spell out what each one does (recover vs backfill). -->
+  <div class="fc-src-actions">
+    <v-btn
+      icon size="small" variant="text" :loading="checking"
+      @click.stop="emit('check', source)"
+    >
+      <v-icon>mdi-play</v-icon>
+      <v-tooltip activator="parent" location="top">
+        Check now — fetch posts published since the last check
+      </v-tooltip>
+    </v-btn>
+    <v-btn
+      icon size="small" variant="text"
+      :color="running ? 'warning' : undefined"
+      @click.stop="emit('backfill', source)"
+    >
+      <v-icon>{{ running ? 'mdi-stop' : 'mdi-magnify-scan' }}</v-icon>
+      <v-tooltip activator="parent" location="top">
+        {{ running
+          ? (recovering ? 'Stop recovery' : 'Stop backfill')
+          : 'Backfill — one-time walk of the FULL post history until complete' }}
+      </v-tooltip>
+    </v-btn>
+
+    <v-menu location="bottom end">
+      <template #activator="{ props: menuProps }">
+        <v-btn icon size="small" variant="text" v-bind="menuProps" @click.stop>
+          <v-icon>mdi-dots-vertical</v-icon>
+          <v-tooltip activator="parent" location="top">More actions</v-tooltip>
+        </v-btn>
+      </template>
+      <v-list density="compact" min-width="260">
+        <v-list-item
+          v-if="isPatreon && !running"
+          prepend-icon="mdi-eye-outline"
+          @click="emit('preview', source)"
+        >
+          <v-list-item-title>Preview backfill</v-list-item-title>
+          <v-list-item-subtitle>
+            Count what a backfill would download — nothing is downloaded
+          </v-list-item-subtitle>
+        </v-list-item>
+        <v-list-item
+          v-if="isPatreon && !running"
+          prepend-icon="mdi-backup-restore"
+          @click="emit('recover', source)"
+        >
+          <v-list-item-title>Recover dropped near-duplicates</v-list-item-title>
+          <v-list-item-subtitle>
+            Re-fetch images previously dropped as near-dups and re-judge them
+            under the current similarity threshold
+          </v-list-item-subtitle>
+        </v-list-item>
+        <v-divider v-if="isPatreon && !running" />
+        <v-list-item
+          base-color="error"
+          prepend-icon="mdi-delete-outline"
+          @click="emit('remove', source)"
+        >
+          <v-list-item-title>Remove source</v-list-item-title>
+        </v-list-item>
+      </v-list>
+    </v-menu>
+  </div>
+</template>
+
+<script setup>
+import { computed } from 'vue'
+
+const props = defineProps({
+  source: { type: Object, required: true },
+  checking: { type: Boolean, default: false },
+})
+const emit = defineEmits(['check', 'backfill', 'recover', 'preview', 'remove'])
+
+const running = computed(() => props.source.backfill_state === 'running')
+const recovering = computed(() => !!props.source.backfill_bypass_seen)
+const isPatreon = computed(() => props.source.platform === 'patreon')
+</script>
+
+<style scoped>
+.fc-src-actions {
+  display: inline-flex;
+  align-items: center;
+  gap: 2px;
+}
+</style>