Fix file sharing load speed and move error; misc updates

- Remove recursive directory size calculations (single Seafile API call per list)
- Remove 'Used in this location' usage display
- Fix move using v2 per-type endpoints instead of broken batch endpoint
- Send entry type from frontend for correct move routing

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

supabase/migrations/20260420153000_remove_external_company_memberships.sql

@@ -0,0 +1,9 @@
+delete from public.company_members cm
+using public.profiles p
+where p.id = cm.profile_id
+  and p.role = 'external';
+
+update public.profiles
+set company_id = null
+where role = 'external'
+  and company_id is not null;