feat(checkin): open reference-parity details modal from signed buttons

- Rebuild checkin details modal HTML 1:1 with reference theme:
  colorful header c-blue, user card (points/level), daily reward
  card and 7-day continuous mini cards
- Signed entry buttons (header dropdown, user-card badge, user
  center) become clickable checkin-details-link modal triggers
  instead of disabled buttons
- Swap data-signin-btn to details link in place after successful
  signin (reference .initiate-checkin replacement behavior)
- Add aksrt-checkin-details-modal runtime shell (modal-mini 400px)
- Remove dead code: legacy lite modal, admin-ajax details handler,
  /signin/history route, signin calendar; rebuild public bundles
- Update contract tests to the new checkin modal contract

tests/widget-system/toast-contract.test.cjs

@@ -253,7 +253,7 @@ test('balance center actions use direct fixed-id notyf flows', () => {
   assert.match(headerUserbox, /data-signin-btn[\s\S]*?data-signin-label/);
   assert.match(headerUserbox, /add_action\('wp_footer', 'aksrt_render_signin_captcha'\)/);
   assert.match(headerUserbox, /data-signin-captcha[\s\S]*?aksrt_render_captcha\('signin'\)/);
-  assert.match(signinService, /aksrt-checkin-modal__btn[^>]+data-signin-btn/);
+  assert.match(signinService, /but c-blue ml10 p2-10 radius" data-signin-btn/);
   assert.doesNotMatch(headerUserbox + signinService, /data-aksrt-checkin/);
   assert.match(context, /'signin_enabled'\s*=>\s*\$signin_enabled/);
   assert.match(context, /'signin_signed_today'\s*=>\s*\$signin_signed_today/);