all: delete the code nothing calls

From the audit (#5178). Each was unreachable from every client:

- Checklist add-item and delete-item: REST POST /items and DELETE /items/<id>,
  the Tauri commands, the store, rest and local adapters, the core's
  add_item/delete_item, set_item_text and remove_item, and the FFI exports.
  Adding, rewording and removing an item are body edits in every editor. The
  checked toggle stays, and its rewriter is simpler without the drop branch.
- Manual unfurl: POST /unfurl and its adapters. Previews arrive in the
  background after a save (unfurl_queue).
- The /api/config `android_client` key, android_release() and the
  APK_NAME/MANIFEST_NAME aliases. Phones poll /api/client/android.
- users.email_verified and users.avatar_path (migration 0037). Nothing set
  the first or read the second; the SMTP reset never checked verification.
- derive::extract_tags (only tests used it; the shared fixture now runs
  through extract_tag_spans), the unused check and link icons, and the
  unused editor_add_item string.
- The blob scheme is renamed tsblob -> inkblob. URLs are built as notes are
  read, so nothing stored carries the old one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/Icon.vue

@@ -13,7 +13,6 @@ const paths: Record<string, string> = {
   tag: '<path d="M12.586 2.586A2 2 0 0 0 11.172 2H4a2 2 0 0 0-2 2v7.172a2 2 0 0 0 .586 1.414l8.704 8.704a2.426 2.426 0 0 0 3.42 0l6.58-6.58a2.426 2.426 0 0 0 0-3.42z"/><circle cx="7.5" cy="7.5" r=".5" fill="currentColor"/>',
   pencil: '<path d="M21.174 6.812a1 1 0 0 0-3.986-3.987L3.842 16.174a2 2 0 0 0-.5.83l-1.321 4.352a.5.5 0 0 0 .623.622l4.353-1.32a2 2 0 0 0 .83-.497z"/><path d="m15 5 4 4"/>',
   plus: '<path d="M5 12h14"/><path d="M12 5v14"/>',
-  check: '<path d="M20 6 9 17l-5-5"/>',
   checkbox: '<rect width="18" height="18" x="3" y="3" rx="2"/><path d="m9 12 2 2 4-4"/>',
   image: '<rect width="18" height="18" x="3" y="3" rx="2"/><circle cx="9" cy="9" r="2"/><path d="m21 15-3.086-3.086a2 2 0 0 0-2.828 0L6 21"/>',
   bell: '<path d="M10.268 21a2 2 0 0 0 3.464 0"/><path d="M3.262 15.326A1 1 0 0 0 4 17h16a1 1 0 0 0 .74-1.673C19.41 13.956 18 12.499 18 8A6 6 0 0 0 6 8c0 4.499-1.411 5.956-2.738 7.326"/>',
@@ -27,7 +26,6 @@ const paths: Record<string, string> = {
   device: '<rect width="14" height="20" x="5" y="2" rx="2" ry="2"/><path d="M12 18h.01"/>',
   sync: '<path d="M3 12a9 9 0 0 1 9-9 9.75 9.75 0 0 1 6.74 2.74L21 8"/><path d="M21 3v5h-5"/><path d="M21 12a9 9 0 0 1-9 9 9.75 9.75 0 0 1-6.74-2.74L3 16"/><path d="M3 21v-5h5"/>',
   paperclip: '<path d="m21.44 11.05-9.19 9.19a6 6 0 0 1-8.49-8.49l8.57-8.57A4 4 0 1 1 18 8.84l-8.59 8.57a2 2 0 0 1-2.83-2.83l8.49-8.48"/>',
-  link: '<path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"/><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"/>',
   filter: '<polygon points="22 3 2 3 10 12.46 10 19 14 21 14 12.46 22 3"/>',
   users: '<path d="M16 21v-2a4 4 0 0 0-4-4H6a4 4 0 0 0-4 4v2"/><circle cx="9" cy="7" r="4"/><path d="M22 21v-2a4 4 0 0 0-3-3.87"/><path d="M16 3.13a4 4 0 0 1 0 7.75"/>',
   copy: '<rect width="14" height="14" x="8" y="8" rx="2" ry="2"/><path d="M4 16c-1.1 0-2-.9-2-2V4c0-1.1.9-2 2-2h10c1.1 0 2 .9 2 2"/>',