fix(modal): kebab menus render BEHIND the modal — bump z-index above it

THE actual root cause of the "dead" tag-chip kebab (operator inspected it
2026-06-07: the menu was ghosted, blurred, behind the sidebar). The teleported
v-menu landed below .fc-viewer (z-index 2000) and the modal's
backdrop-filter: blur(8px) smeared it — so it opened the whole time, just
underneath. Every prior "fix" (un-nesting the button, the explicit activator
pattern) was chasing a click/activation problem that never existed.

Set :z-index="2400" on the tag-chip and suggestion kebab menus so they paint
above the modal. (Dialogs already render on top — only the anchored menus tied
with the modal's z-index and lost.)

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

frontend/src/components/modal/SuggestionItem.vue

@@ -37,6 +37,7 @@
       />
       <v-menu
         v-model="menuOpen" activator="parent" :open-on-click="false"
+        :z-index="2400"
       >
         <v-list density="compact">
           <v-list-item @click="$emit('alias', suggestion)">

frontend/src/components/modal/TagChip.vue

@@ -21,7 +21,11 @@
         :aria-label="`More actions for ${tag.name}`"
         @click.stop="menuOpen = !menuOpen"
       />
-      <v-menu v-model="menuOpen" activator="parent" :open-on-click="false">
+      <!-- :z-index above the modal's 2000 — the teleported menu otherwise lands
+           BEHIND .fc-viewer and gets blurred by its backdrop-filter (operator
+           saw it ghosted behind the sidebar, 2026-06-07). THIS is what made the
+           kebab look dead the whole time: it opened, just underneath. -->
+      <v-menu v-model="menuOpen" activator="parent" :open-on-click="false" :z-index="2400">
         <v-list density="compact">
           <v-list-item @click="$emit('rename', tag)">
             <v-list-item-title>Rename…</v-list-item-title>