refactor(ui): consolidate 7 hand-rolled kebabs into one KebabMenu (DRY pattern sweep)

First pattern-consistency DRY pass (process #594). The overflow kebab was
hand-rolled 7 ways in two divergent activator strategies — Pattern A
(#activator + v-bind) which silently breaks inside the teleported image modal
(#711), and Pattern B (manual v-model + activator=parent + open-on-click=false +
z-index 2400) the modal kebabs needed as a workaround.

New <KebabMenu> (components/common) bakes in the modal-safe strategy
UNIVERSALLY, so every kebab works in modal and non-modal contexts — folding the
latent #711-class bug fix into all five Pattern-A sites. Menu items go in the
default slot; variations (size/variant/location/label/min-width) are props.

Adopted across all 7: TagChip, SuggestionItem, TagCard, SeriesView card,
SeriesManageView, BackupRunsTable, SourceActions. Exhaustiveness (§8b):
mdi-dots-vertical now lives only in KebabMenu. Labeled dropdowns / nav menus /
filter popovers are a different concept and left alone. Seeded the pattern
catalog so new code reuses the primitive. Test: KebabMenu renders slot items +
trigger label/glyph + presentational props.

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

frontend/src/components/settings/BackupRunsTable.vue

@@ -30,25 +30,20 @@
           <span v-else class="fc-muted">—</span>
         </td>
         <td class="text-right">
-          <v-menu>
-            <template #activator="{ props: act }">
-              <v-btn icon="mdi-dots-vertical" size="x-small" variant="text" v-bind="act" />
-            </template>
-            <v-list density="compact">
-              <v-list-item
-                :title="r.tag ? 'Untag' : 'Tag…'"
-                @click="$emit('tag', r)"
-              />
-              <v-list-item
-                title="Restore…" :disabled="r.status !== 'ok'"
-                @click="$emit('restore', r)"
-              />
-              <v-list-item
-                title="Delete…"
-                @click="$emit('delete', r)"
-              />
-            </v-list>
-          </v-menu>
+          <KebabMenu :label="`Actions for backup ${r.id}`">
+            <v-list-item
+              :title="r.tag ? 'Untag' : 'Tag…'"
+              @click="$emit('tag', r)"
+            />
+            <v-list-item
+              title="Restore…" :disabled="r.status !== 'ok'"
+              @click="$emit('restore', r)"
+            />
+            <v-list-item
+              title="Delete…"
+              @click="$emit('delete', r)"
+            />
+          </KebabMenu>
         </td>
       </tr>
       <tr v-if="!runs.length">
@@ -60,6 +55,7 @@
 
 <script setup>
 import { formatRelative as fmtRelative } from '../../utils/date.js'
+import KebabMenu from '../common/KebabMenu.vue'
 
 defineProps({ runs: { type: Array, default: () => [] } })
 defineEmits(['restore', 'delete', 'tag'])