refactor: move action bar to top and lighten styling

- Moved PlanActionBar from fixed bottom to sticky top below GroupView
- Removed position: fixed and bottom padding workaround
- Action bar now uses lighter bg (#fafafa), thinner padding, border-bottom
- Removed unused padding-bottom: 100px from .plan, reduced to 24px

public/src/components/PlanActionBar.vue

@@ -25,12 +25,12 @@ const props = defineProps<{
 <style scoped lang="less">
 
 .action-bar {
-    width: calc(100% - 32px * 2);
-    border-top: 1px solid #d7d5d5;
+    width: calc(100% - 24px * 2);
     display: flex;
-    padding: 10px 32px;
-    background: #ffffff;
+    padding: 6px 24px;
+    background: #fafafa;
     justify-content: flex-end;
+    border-bottom: 1px solid #e0e0e0;
 
     .other-action{
         transition: 200ms translate;