llm-proxy(ui): 修 placeholder token 泄漏 + UI 重做 + λ favicon

- 修：token 输入框 placeholder 之前硬编码了真实 token (`e.g.
  famzheng-llm-2026`)，等于明文泄露。改成 `your auth token`
- UI 重做 — 100dvh 锁 viewport（处理移动软键盘）+ grid 布局
  让 thread 永远占中间、footer 永远贴底
- textarea autogrow（最高 200px，超出内部滚）
- 复制按钮 / smooth scroll-to-bottom (double rAF) /
  iOS momentum scroll / safe-area padding
- 错误状态独立 row，monospace + 红底
- λ favicon（紫蓝渐变 + 绿色在线点 + glow）— SVG include_str!
  进 binary，`/favicon.svg` + `/favicon.ico` 同源响应

apps/llm-proxy/src/main.rs

@@ -37,6 +37,8 @@ async fn main() -> std::io::Result<()> {
         .route("/healthz", get(|| async { "ok" }))
         .route("/", get(|| async { Redirect::permanent("/chat") }))
         .route("/chat", get(chat_ui))
+        .route("/favicon.svg", get(favicon))
+        .route("/favicon.ico", get(favicon)) // 浏览器默认会请求 .ico，让它共享同一 SVG
         .merge(chat_api)
         .layer(TraceLayer::new_for_http());
 
@@ -47,11 +49,22 @@ async fn main() -> std::io::Result<()> {
 }
 
 const CHAT_HTML: &str = include_str!("../web/chat.html");
+const FAVICON_SVG: &str = include_str!("../web/favicon.svg");
 
 async fn chat_ui() -> Html<&'static str> {
     Html(CHAT_HTML)
 }
 
+async fn favicon() -> impl IntoResponse {
+    (
+        [
+            (axum::http::header::CONTENT_TYPE, "image/svg+xml"),
+            (axum::http::header::CACHE_CONTROL, "public, max-age=604800"),
+        ],
+        FAVICON_SVG,
+    )
+}
+
 /// 验 `Authorization: token <PROXY_AUTH_TOKEN>`，错的直接 401。
 async fn require_token(
     State(cfg): State<Arc<proxy::Config>>,

apps/llm-proxy/web/chat.html

@@ -4,6 +4,7 @@
 <meta charset="UTF-8" />
 <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
 <meta name="theme-color" content="#0f1419" />
+<link rel="icon" type="image/svg+xml" href="/favicon.svg" />
 <title>llm.famzheng.me</title>
 <style>
   :root {

apps/llm-proxy/web/favicon.svg

@@ -0,0 +1,18 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <defs>
+    <linearGradient id="bg" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0%" stop-color="#7c3aed"/>
+      <stop offset="100%" stop-color="#06b6d4"/>
+    </linearGradient>
+    <filter id="glow">
+      <feGaussianBlur stdDeviation="1.2"/>
+    </filter>
+  </defs>
+  <rect x="2" y="2" width="60" height="60" rx="14" fill="url(#bg)"/>
+  <text x="32" y="46" text-anchor="middle"
+        font-family="ui-serif, Georgia, 'Times New Roman', serif"
+        font-size="42" font-weight="700" fill="white"
+        style="font-style: italic;">λ</text>
+  <circle cx="49" cy="49" r="6.5" fill="#4ade80" filter="url(#glow)" opacity="0.5"/>
+  <circle cx="49" cy="49" r="4.5" fill="#4ade80"/>
+</svg>