fix(polish): 订单购物车论坛粉边软化 + 论坛付费帖购链路

- 购物车/商品/论坛表面复用 #77 soft recipe（mix 边 + soft ring）
- 论坛 visibility=pay：订单 resource + 余额扣费闭环
- VIP 价/免费解锁 + 购买 CTA/AJAX，复用现有 Order/Credits

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/css/frontend/forum/extras/base.css

@@ -253,7 +253,7 @@
 
 .aksrt-forum-topic__badge--question {
     background: #e6f7ff;
-    color: #1890ff;
+    color: var(--color-primary);
 }
 
 .aksrt-forum-topic__badge--solved {
@@ -263,7 +263,7 @@
 
 .aksrt-forum-topic-item__badge--question {
     background: #e6f7ff;
-    color: #1890ff;
+    color: var(--color-primary);
 }
 
 .aksrt-forum-topic-item__badge--solved {
@@ -328,8 +328,8 @@
 }
 
 .aksrt-forum-topic__score-btn:hover:not(:disabled) {
-    border-color: var(--color-primary, #1890ff);
-    color: var(--color-primary, #1890ff);
+    border-color: color-mix(in srgb, var(--color-primary) 45%, var(--color-line, #e5e7eb));
+    color: var(--color-primary);
 }
 
 .aksrt-forum-topic__score-btn--up:hover:not(:disabled) {
@@ -372,7 +372,7 @@
 .aksrt-forum-topic__vote-type-badge {
     display: inline-block;
     padding: 1px 6px;
-    background: var(--color-primary, #1890ff);
+    background: var(--color-primary);
     color: #fff;
     border-radius: var(--radius-pill, 999px);
     font-size: 11px;
@@ -401,7 +401,7 @@
 
 .aksrt-forum-topic__chip--topic-cat {
     background: var(--color-primary-bg, #e6f7ff);
-    color: var(--color-primary, #1890ff);
+    color: var(--color-primary);
     font-weight: 600;
 }