fix(secure-context): full audit — DestructiveConfirmModal.expectedTokenOverride + bulk-delete + min-dim use backend-computed tokens

Operator-flagged 2026-05-27: walk the whole project for the same shape
as the min-dim Delete-button silent failure (crypto.subtle TypeError
on plain HTTP). FC runs over plain HTTP per the homelab posture;
Secure-Context-gated browser APIs are undefined on the production
origin.

**Audit results across `frontend/src/`:**

  crypto.subtle.digest        — 2 sites:
    - MinDimensionCard (fixed 2026-05-27)
    - BulkEditorPanel (THIS FIX)
  navigator.clipboard         — 1 site, already guarded:
    - utils/clipboard.js writeText with execCommand fallback
  serviceWorker / mediaDevices / Push / Web USB|HID|Bluetooth|Serial /
  cookieStore / queryLocalFonts / WebAuthn / geolocation
                              — NOT USED, nothing to fix

  Extension scripts (background.js) use crypto.subtle but run from
  moz-extension:// which IS a Secure Context — left as-is.

**BulkEditorPanel double bug**

The bulk-delete UI on the gallery selection had been broken since
FC-3k shipped, in two ways:

1. `crypto.subtle.digest` swallowed TypeError on plain HTTP — modal
   never opened. Same symptom as min-dim.
2. Even on HTTPS, the modal's `kind="images-selection"` produced
   `delete-images-selection-<sha8>` while the backend expected
   `delete-images-<sha8>`. The two would never match.

Fix:

- Backend `/api/admin/images/bulk-delete` dry-run response now returns
  `confirm_token` (the canonical `delete-images-<sha8>` string).
  Integration test `test_bulk_delete_dry_run_returns_counts` pinned to
  assert the new field.
- DestructiveConfirmModal gains an `expectedTokenOverride` prop. When
  set, it bypasses the `${action}-${kind}-${runId}` formula and uses
  the explicit string. This decouples the UI label (`kind`) from the
  wire-format token (server-provided), so future endpoints can use a
  kind-specific label without their kind name leaking into the token.
- BulkEditorPanel passes `:expected-token-override="bulkProjected?.confirm_token"`
  — no client-side crypto, no kind-prefix mismatch.
- MinDimensionCard refactored to the same explicit pattern (was
  slicing the 8-char suffix off the backend's token and passing it
  through `runId`; now passes the full backend token via
  `expected-token-override` directly). Cleaner; one source of truth.

**Banked memory**

`feedback_no_secure_context_apis.md` documents the full table of
Secure-Context-gated APIs, which ones FC currently uses, and how each
is handled. Indexed in MEMORY.md. Sites for the audit also listed in
the memory for future drift-checking.

No other Secure-Context-gated APIs found in `frontend/src/`. The same
shape won't recur unless someone adds a new dependency on one — at
which point the banked memory should fire.

frontend/src/components/cleanup/MinDimensionCard.vue

@@ -52,8 +52,8 @@
       v-model="showModal"
       action="delete"
       kind="min-dim"
-      :run-id="tokenSuffix"
       tier="C"
+      :expected-token-override="preview?.confirm_token || ''"
       :projected-counts="projectedCounts"
       :description="`Width < ${minW} OR height < ${minH}`"
       @confirm="onConfirmedDelete"
@@ -62,11 +62,19 @@
 </template>
 
 <script setup>
-import { computed, onMounted, ref } from 'vue'
+import { onMounted, ref } from 'vue'
 
 import DestructiveConfirmModal from '../modal/DestructiveConfirmModal.vue'
 import { useCleanupStore } from '../../stores/cleanup.js'
 
+// Backend's preview response hands the full Tier-C confirm token back
+// as `confirm_token` (e.g. `delete-min-dim-1a2b3c4d`); passed straight
+// to the modal via `expected-token-override`. We previously
+// reconstructed via Web Crypto's SHA-256, but `crypto.subtle` is
+// Secure-Context-gated and undefined on plain-HTTP origins, so the
+// Delete button silently swallowed the TypeError. Operator-flagged
+// 2026-05-27.
+
 const store = useCleanupStore()
 const minW = ref(0)
 const minH = ref(0)
@@ -75,21 +83,6 @@ const busy = ref(false)
 const showModal = ref(false)
 const projectedCounts = ref({})
 
-// The backend hands the full Tier-C confirm token back with the
-// preview response (e.g. `delete-min-dim-1a2b3c4d`). We previously
-// reconstructed it client-side via Web Crypto's SHA-256, but
-// `crypto.subtle` is undefined on plain-HTTP origins (homelab posture)
-// and the Delete-button click handler was silently swallowing the
-// TypeError. Letting the backend own the token is also the single
-// source of truth — frontend just splits off the 8-char suffix to
-// feed DestructiveConfirmModal's `runId` slot (the modal templates
-// the prefix `delete-min-dim-` itself from action+kind).
-const tokenSuffix = computed(() => {
-  const full = preview.value?.confirm_token ?? ''
-  // `delete-min-dim-1a2b3c4d` → `1a2b3c4d`
-  return full.startsWith('delete-min-dim-') ? full.slice('delete-min-dim-'.length) : ''
-})
-
 onMounted(async () => {
   await store.loadDefaults()
   minW.value = store.defaults.min_width