修复：自适应 UI — 消除右侧溢出和顶部空白区域

- App.svelte: 将 .app-shell 宽度从 100vw 改为 100% 避免滚动条溢出
- App.svelte: 重置 body 的上下左右内边距，消除全局样式造成的无用空白
- App.svelte: 添加 html 和 .app-header 的 overflow:hidden 容器约束
- ConfigPanel.svelte: 将 h2 标题截断规则（flex:1/min-width:0/overflow:hidden）从 ≤600px 提升到基础样式，避免长 Bot ID 挤出保存按钮
- ConfigPanel.svelte: 为 .config-header 添加 overflow:hidden+min-width:0，为 .save-btn 添加 flex-shrink:0
- 清理空的 @media (max-width: 1280px) 块

Author: RainyN0077

frontend/src/App.svelte

@@ -121,15 +121,22 @@
         box-sizing: border-box;
     }
 
+    :global(html) {
+        overflow: hidden;
+    }
+
     :global(body) {
         overflow: hidden;
+        padding-top: 0;
+        padding-left: 0;
+        padding-right: 0;
     }
 
     .app-shell {
         display: flex;
         flex-direction: column;
         height: 100vh;
-        width: 100vw;
+        width: 100%;
         overflow: hidden;
     }
 
@@ -145,6 +152,7 @@
         z-index: 100;
         flex-shrink: 0;
         height: 46px;
+        overflow: hidden;
     }
 
     .header-left {

frontend/src/pages/ConfigPanel.svelte

@@ -1106,6 +1106,8 @@ async function resetFont() {
         align-items: center;
         margin-bottom: 1rem;
         flex-shrink: 0;
+        overflow: hidden;
+        min-width: 0;
     }
 
     .config-header h2 {
@@ -1117,6 +1119,11 @@ async function resetFont() {
         background: linear-gradient(135deg, rgba(31, 139, 214, .1), rgba(24, 138, 81, .08));
         border: 1px solid rgba(15, 23, 42, .08);
         box-shadow: var(--shadow-soft);
+        flex: 1;
+        min-width: 0;
+        overflow: hidden;
+        text-overflow: ellipsis;
+        white-space: nowrap;
     }
 
     .save-btn {
@@ -1126,6 +1133,7 @@ async function resetFont() {
         font-size: .95rem;
         font-weight: 600;
         border-radius: 10px;
+        flex-shrink: 0;
     }
 
     .save-btn:disabled {
@@ -1471,9 +1479,6 @@ async function resetFont() {
         flex-wrap: wrap;
     }
 
-    @media (max-width: 1280px) {
-    }
-
     @media (max-width: 900px) {
         .config-panel {
             padding: .75rem 1rem;
@@ -1546,11 +1551,6 @@ async function resetFont() {
         .config-header h2 {
             font-size: .85rem;
             padding: .35rem .6rem;
-            flex: 1;
-            min-width: 0;
-            overflow: hidden;
-            text-overflow: ellipsis;
-            white-space: nowrap;
         }
 
         .save-btn {