fix(export): restore virtualized contacts list and sticky controls

src/pages/ExportPage.scss

@@ -859,6 +859,7 @@
   display: inline-flex;
   align-items: center;
   gap: 6px;
+  margin: 8px 12px 0;
   padding: 6px 10px;
   border-radius: 999px;
   background: rgba(var(--primary-rgb), 0.1);
@@ -874,6 +875,9 @@
   align-items: flex-start;
   gap: 12px;
   flex-wrap: wrap;
+  padding: 10px 12px;
+  border-bottom: 1px solid color-mix(in srgb, var(--border-color) 85%, transparent);
+  background: color-mix(in srgb, var(--bg-primary) 82%, var(--bg-secondary));
 }
 
 .table-cache-meta {
@@ -990,17 +994,24 @@
   --contacts-select-col-width: 34px;
   --contacts-message-col-width: 120px;
   --contacts-action-col-width: 280px;
-  overflow: visible;
+  overflow: hidden;
   border: 1px solid var(--border-color);
   border-radius: 10px;
   min-height: 320px;
   height: auto;
-  flex: 0 0 auto;
+  flex: 1;
   display: flex;
   flex-direction: column;
 }
 
 .table-wrap {
+  .session-table-sticky {
+    position: sticky;
+    top: 0;
+    z-index: 20;
+    background: var(--card-bg);
+  }
+
   .loading-state,
   .empty-state {
     flex: 1;
@@ -1151,12 +1162,27 @@
   }
 
   .contacts-list {
-    flex: 0 0 auto;
-    min-height: auto;
-    overflow: visible;
+    flex: 1;
+    min-height: 360px;
+    height: clamp(360px, 62vh, 760px);
+    overflow: hidden;
     padding: 0 12px 12px;
   }
 
+  .contacts-virtuoso {
+    height: 100%;
+
+    &::-webkit-scrollbar {
+      width: 6px;
+    }
+
+    &::-webkit-scrollbar-thumb {
+      background: var(--text-tertiary);
+      border-radius: 3px;
+      opacity: 0.3;
+    }
+  }
+
   .contacts-selection-toolbar {
     display: flex;
     align-items: center;
@@ -1381,6 +1407,28 @@
   }
 }
 
+.back-to-top-btn {
+  position: fixed;
+  top: 14px;
+  right: 18px;
+  z-index: 120;
+  border: 1px solid rgba(var(--primary-rgb), 0.4);
+  border-radius: 999px;
+  background: color-mix(in srgb, var(--bg-primary) 90%, var(--bg-secondary));
+  color: var(--primary);
+  font-size: 12px;
+  font-weight: 600;
+  padding: 6px 12px;
+  cursor: pointer;
+  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.18);
+  transition: transform 0.12s ease, box-shadow 0.12s ease;
+
+  &:hover {
+    transform: translateY(-1px);
+    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.2);
+  }
+}
+
 .table-virtuoso {
   height: 100%;
 }
@@ -2354,7 +2402,7 @@
   overflow-y: auto;
   border-radius: 12px;
   border: 1px solid var(--border-color);
-  background: var(--card-bg);
+  background: var(--bg-secondary-solid, var(--bg-primary));
   padding: 12px;
   display: flex;
   flex-direction: column;
@@ -2662,6 +2710,8 @@
 
   .table-wrap .contacts-list {
     padding: 0 10px 10px;
+    min-height: 300px;
+    height: min(56vh, 560px);
   }
 
   .table-wrap .row-message-count {
@@ -2726,4 +2776,9 @@
   .export-session-detail-panel {
     width: calc(100vw - 12px);
   }
+
+  .back-to-top-btn {
+    top: 10px;
+    right: 10px;
+  }
 }