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

assets/js/enhancements2.js

@@ -241,41 +241,6 @@
     });
   }
 
-  /* ============================================================
-   * 8. 签到日历可视化
-   * ============================================================ */
-  function initSigninCalendar() {
-    var calendar = document.querySelector('[data-aksrt-signin-calendar]');
-    if (!calendar) return;
-
-    var data = [];
-    try {
-      data = JSON.parse(calendar.dataset.aksrtSigninCalendar || '[]');
-    } catch (e) {}
-
-    // 生成最近 30 天的格子
-    var today = new Date();
-    var html = '<div class="aksrt-signin-calendar__grid">';
-
-    for (var i = 29; i >= 0; i--) {
-      var d = new Date(today);
-      d.setDate(d.getDate() - i);
-      var dateStr = d.toISOString().split('T')[0];
-      var isSigned = data.indexOf(dateStr) !== -1;
-      var isToday = i === 0;
-
-      html += '<div class="aksrt-signin-calendar__day' +
-        (isSigned ? ' is-signed' : '') +
-        (isToday ? ' is-today' : '') +
-        '" title="' + dateStr + (isSigned ? ' ✓' : '') + '">' +
-        '<span>' + d.getDate() + '</span>' +
-        '</div>';
-    }
-
-    html += '</div>';
-    calendar.innerHTML = html;
-  }
-
   /* ============================================================
    * 初始化入口 — 先执行一次，随后监听 auto_fun 重扫（各 init 幂等）
    * ============================================================ */
@@ -286,7 +251,6 @@
     initSticky();
     initParallax();
     initFloatLabels();
-    initSigninCalendar();
   }
 
   if (document.readyState === 'loading') {