feat(account): unlink game accounts on the shard before an account is deleted (MODULE_API 1.20.0)

ACCOUNT_DELETION.md §4.4 (AD10, AD11). api.onUserDeleting queues every linked
account in the new shard_pending_unlinks table, then calls the sidecar's
DELETE /link/{account} (actor web:account-deletion) and drops the mirror on 200/404.
A shard that is away leaves the row pending, retried on WS reconnect and on a live
server.hello; a protected account (403) is refused and listed on Admin -> Shard as
still linked on the shard. A live mob.login without the deleted user's webId clears
the row. coreApi ^1.20.0; core-ref pinned to website#232's merge (7bd93b8).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

module.json

@@ -2,7 +2,7 @@
   "id": "uo",
   "name": "Ultima Online",
   "version": "0.6.0",
-  "coreApi": "^1.10.0",
+  "coreApi": "^1.20.0",
   "server": "server/index.js",
   "client": { "entry": "client/dist/entry.js" },
   "schema": "server/db/schema.sql",