feat: admin org management API + member login fixes

Add NestJS endpoints the admin panel org UI was calling (all returning 404):
- GET/POST /admin/orgs — list and create organizations
- GET /admin/orgs/:id — org detail with tenants and orgAdmins
- POST /admin/orgs/:id/admins — create OrgAdmin with hashed password
- PATCH /admin/tenants/:id/org — assign/unassign tenant from org

Also ship the member login page and sidebar fix from the previous session:
- Move /my/login to /member-login to break infinite redirect loop
- Add /member-login to PUBLIC_PATHS in sidebar so it is not intercepted

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

apps/web/app/_lib/sidebar.tsx

@@ -22,7 +22,7 @@ const SUPER_ADMIN_LINKS = [
   { href: '/admin/drafts', label: 'AI Drafts' },
 ];
 
-const PUBLIC_PATHS = ['/login', '/signup', '/onboard'];
+const PUBLIC_PATHS = ['/login', '/signup', '/onboard', '/member-login'];
 const ADMIN_PATHS = ['/admin'];
 const MEMBER_PATHS = ['/my'];