fix(mobile): flex-center pill buttons and fix learning task card layout

- learning: task-list/snippet-list use column direction (row squeeze caused
  one-char-per-line vertical text in today-task cards)
- learning/profile: fold-toggle flex-centered
- login: code-button flex-centered
- practice: transcript-toggle / bubble-action / style-chip flex-centered
- questions: filter-chip flex-centered
- sop: modal-close flex-centered with 32px hit area
- web-ai: bubble-action flex-centered

mobile-uni/src/pages/user/learning/index.vue

@@ -1055,7 +1055,13 @@ onUnload(invalidateRequests);
 }
 
 .task-list,
-.snippet-list,
+.snippet-list {
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+  margin-top: 14px;
+}
+
 .action-list {
   display: flex;
   gap: 10px;
@@ -1209,17 +1215,19 @@ onUnload(invalidateRequests);
 }
 
 .fold-toggle {
-  display: block;
+  display: flex;
+  align-items: center;
+  justify-content: center;
   width: 100%;
+  min-height: 36px;
   margin: 10px 0 0;
-  padding: 8px 0;
+  padding: 0;
   border: none;
   border-top: 1px dashed #eceff2;
   background: transparent;
   color: #6b7480;
   font-size: 13px;
-  text-align: center;
-  line-height: 1.5;
+  line-height: 1.3;
 }
 
 .fold-toggle::after {