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/sop/index.vue

@@ -1357,6 +1357,9 @@ onUnload(() => {
 }
 
 .modal-close {
+  display: flex;
+  align-items: center;
+  justify-content: center;
   background: transparent;
   border: none;
   font-size: 24px;
@@ -1364,8 +1367,9 @@ onUnload(() => {
   cursor: pointer;
   padding: 0;
   line-height: 1;
-  width: auto;
-  min-height: auto;
+  width: 32px;
+  height: 32px;
+  min-height: 32px;
 }
 
 .modal-body {