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>

alembic/versions/0037_drop_unused_user_fields.py

@@ -0,0 +1,38 @@
+"""users: drop email_verified and avatar_path, which nothing used
+
+Revision ID: 0037
+Revises: 0036
+Create Date: 2026-10-07
+
+Both came with the foundation (0001) for features that were never built (#5178).
+Nothing ever set `email_verified`, so it was false for every account on the server
+while the offline desktop reported it as true; nothing read or wrote `avatar_path`.
+A field whose value means nothing is worse than no field: a later feature would
+trust it. If address verification is ever built, it adds its own column, with a
+migration that says what the existing accounts are.
+
+## Downgrade
+
+Adds both columns back empty: every account unverified, no avatar. That is what
+they held before.
+"""
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0037"
+down_revision = "0036"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.drop_column("users", "email_verified")
+    op.drop_column("users", "avatar_path")
+
+
+def downgrade() -> None:
+    op.add_column("users", sa.Column("avatar_path", sa.Text(), nullable=True))
+    op.add_column(
+        "users",
+        sa.Column("email_verified", sa.Boolean(), nullable=False, server_default=sa.false()),
+    )