fix: 输入框置底 — 移除冲突的 height 属性，用 align center bottom

grid-rows 已设置行高 (auto auto 1fr 5)，CSS height 会与 grid 冲突
改为 align: center bottom 让 Input 贴底

Co-Authored-By: Claude <noreply@anthropic.com>

services/tui_service.py

@@ -560,7 +560,6 @@ class TUIFramework(App):
     }
 
     #monitor-area {
-        height: 3;
         padding: 0 1;
         background: $panel;
         color: $text;
@@ -573,9 +572,9 @@ class TUIFramework(App):
     }
 
     #input-area {
-        height: 5;
         border: solid $secondary;
         padding: 0 1;
+        align: center bottom;
     }
 
     ScrollableContainer {