feat(activity): search/filter on both Activity-tab panes

Recent failures gains a client-side search over the already-loaded 24h
rows (task/queue/target/error), shown as a filtered/total count alongside
the existing error-type chips. All recent activity gains a debounced
server-side task-name search (new `task` ILIKE param on /runs) so it
spans the full history, not just the loaded page. LIKE wildcards are
escaped so task names' literal underscores match literally.

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

frontend/src/components/settings/SystemActivityTab.vue

@@ -21,8 +21,15 @@
     <v-card class="mb-4">
       <CardHeading icon="mdi-alert-circle-outline" title="Recent failures (last 24h)">
         <v-spacer />
-        <span class="text-caption fc-muted">
-          {{ failureCount }} failures
+        <v-text-field
+          v-model="failureSearch"
+          placeholder="Search task, queue, target, error…"
+          density="compact" hide-details clearable
+          prepend-inner-icon="mdi-magnify"
+          style="max-width: 280px;"
+        />
+        <span class="text-caption fc-muted ml-3">
+          {{ filteredFailures.length }} / {{ failureCount }}
         </span>
       </CardHeading>
       <v-card-text>
@@ -77,6 +84,14 @@
     <v-card>
       <CardHeading icon="mdi-format-list-bulleted" title="All recent activity">
         <v-spacer />
+        <v-text-field
+          v-model="filterTask"
+          placeholder="Search task…"
+          density="compact" hide-details clearable
+          prepend-inner-icon="mdi-magnify"
+          style="max-width: 220px;"
+          @update:model-value="onTaskSearch"
+        />
         <v-select
           v-model="filterQueue"
           :items="queueOptions" density="compact" hide-details
@@ -170,6 +185,8 @@ const store = useSystemActivityStore()
 const filterQueue = ref(null)
 const filterStatus = ref(null)
 const filterErrorType = ref(null)
+const filterTask = ref(null)        // server-side task-name search (All activity)
+const failureSearch = ref('')       // client-side search over loaded failures
 
 const queueOptions = [
   { title: 'All queues', value: null },
@@ -225,9 +242,18 @@ const errorTypes = computed(() => {
 const failureCount = computed(() => (store.failures?.recent || []).length)
 
 const filteredFailures = computed(() => {
-  const all = store.failures?.recent || []
-  if (!filterErrorType.value) return all
-  return all.filter(r => r.error_type === filterErrorType.value)
+  let all = store.failures?.recent || []
+  if (filterErrorType.value) {
+    all = all.filter(r => r.error_type === filterErrorType.value)
+  }
+  const q = (failureSearch.value || '').trim().toLowerCase()
+  if (q) {
+    all = all.filter(r =>
+      [r.task_name, r.queue, r.target_id, r.error_type]
+        .some(v => String(v ?? '').toLowerCase().includes(q)),
+    )
+  }
+  return all
 })
 
 function toggleErrorTypeFilter(name) {
@@ -240,9 +266,23 @@ function toggleErrorTypeFilter(name) {
 }
 
 function onFilterChange() {
-  store.setFilter({ queue: filterQueue.value, status: filterStatus.value })
+  store.setFilter({
+    queue: filterQueue.value,
+    status: filterStatus.value,
+    task: (filterTask.value || '').trim() || null,
+  })
   store.loadRuns({ reset: true })
 }
+
+// Server-side search hits the full task_run history, not just the loaded
+// page — debounce so we don't fire a query per keystroke (matches the
+// 300ms idiom in TagsView/AllowlistTable).
+let taskSearchDebounce = null
+function onTaskSearch() {
+  if (taskSearchDebounce) clearTimeout(taskSearchDebounce)
+  taskSearchDebounce = setTimeout(onFilterChange, 300)
+}
+
 function onLoadMore() { store.loadRuns({ reset: false }) }
 function onRefresh() { store.loadRuns({ reset: true }) }