feat(admin): streamline ticket management with dialogs

Move on-behalf ticket creation into a header dialog and load ticket handling on demand. Reuse the admin REST write path, preserve drafts and filters, and cover dialog and server boundaries with regression tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/widget-system/ticket-lifecycle-contract.test.cjs

@@ -28,7 +28,7 @@ test('transition rules live in one place', () => {
   assert.match(body, /if \(\$from === self::KEY_PENDING && \$to === self::KEY_CLOSED\) \{\s*\n\s*return false;/);
 
   // 上层只调用 can_transition，不复制合法性判断。
-  for (const file of ['src/Ticket/TicketStatus.php', 'src/Ticket/TicketRestAdmin.php', 'src/Admin/Native/UsersMenusTicketsCenter.php']) {
+  for (const file of ['src/Ticket/TicketStatus.php', 'src/Ticket/TicketRestAdmin.php', 'src/Admin/Native/UsersMenusTicketsDetail.php']) {
     const src = read(file);
     assert.ok(src.includes('can_transition'), `${file} must delegate to can_transition`);
   }