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/auth/login/index.vue

@@ -461,6 +461,9 @@ onShow(() => {
 }
 
 .code-button {
+  display: flex;
+  align-items: center;
+  justify-content: center;
   width: 100%;
   min-height: 56px;
   padding: 0 4px;
@@ -470,7 +473,7 @@ onShow(() => {
   color: #e60012;
   font-size: 12px;
   font-weight: 700;
-  line-height: 1.3;
+  line-height: 1;
   white-space: nowrap;
   box-shadow: 0 6px 14px rgba(242, 11, 26, 0.06);
 }