feat(files): add Hosted Files admin page at /core/files/

- Search hosted files across all accounts (including disabled)
- Sortable columns, pagination, per-row delete, download, and SHA-256 copy
- Lazy-load file link records per row via /v3/action/hosted_file/{id}/links
- Fix delete to load links first, remove each via correct link_to_type/link_to_id_random,
  then hard-delete with method=delete and rm_orphan=true
- Remove Linked To and Group columns (moved Group/ForType to filter bar only)
- SHA-256 column now visible at lg breakpoint (was xl)
- Added /core/files nav link to /core layout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/core/files/+page.ts

@@ -0,0 +1,5 @@
+import type { PageLoad } from './$types';
+
+export const load: PageLoad = async () => {
+    return {};
+};