fix(frontend): fix remaining Chinese text and background color

packages/frontend/app/home/cloud-docs/FolderTree.tsx

@@ -78,7 +78,7 @@ export default function FolderTree({ onDocClick }: FolderTreeProps) {
       setNewFolderParent(undefined);
       fetchTree();
     } catch {
-      setCreateError("创建文件夹失败，请重试");
+      setCreateError("Failed to create folder, please try again");
     }
   };
 
@@ -139,7 +139,7 @@ export default function FolderTree({ onDocClick }: FolderTreeProps) {
             setNewFolderParent(undefined);
             setNewFolderName("");
           }}
-          title="新建文件夹"
+          title="New folder"
           className="w-6 h-6 flex items-center justify-center rounded hover:bg-gray-200 text-gray-500 hover:text-gray-700 transition-colors"
         >
           <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
@@ -159,7 +159,7 @@ export default function FolderTree({ onDocClick }: FolderTreeProps) {
               if (e.key === "Enter") handleCreateFolder();
               if (e.key === "Escape") setCreatingFolder(false);
             }}
-            placeholder="文件夹名称"
+            placeholder="Folder name"
             className="w-full text-sm px-2 py-1 border border-gray-300 rounded focus:outline-none focus:ring-1 focus:ring-blue-500 mb-1"
           />
           {createError && <p className="text-xs text-red-500 mb-1">{createError}</p>}

packages/frontend/app/home/cloud-docs/__tests__/FolderTree.test.tsx

@@ -110,20 +110,20 @@ describe("FolderTree", () => {
   it("should show create folder form when + button clicked", async () => {
     mockFetch.mockResolvedValueOnce({ ok: true, json: async () => [] });
     render(<FolderTree />);
-    const addBtn = screen.getByTitle("新建文件夹");
+    const addBtn = screen.getByTitle("New folder");
     await userEvent.click(addBtn);
-    expect(screen.getByPlaceholderText("文件夹名称")).toBeInTheDocument();
+    expect(screen.getByPlaceholderText("Folder name")).toBeInTheDocument();
   });
 
   it("should call POST /documents/folder and reload on creation", async () => {
     mockFetch
       .mockResolvedValueOnce({ ok: true, json: async () => [] }) // initial load
       .mockResolvedValueOnce({ ok: true, json: async () => [] }); // reload after create
     render(<FolderTree />);
-    const addBtn = screen.getByTitle("新建文件夹");
+    const addBtn = screen.getByTitle("New folder");
     await userEvent.click(addBtn);
-    const input = screen.getByPlaceholderText("文件夹名称");
-    await userEvent.type(input, "新建文件夹");
+    const input = screen.getByPlaceholderText("Folder name");
+    await userEvent.type(input, "Test Folder");
     await userEvent.click(screen.getByText("创建"));
     await waitFor(() => {
       expect(mockFetch).toHaveBeenCalledWith(
@@ -136,10 +136,10 @@ describe("FolderTree", () => {
   it("should close create form on Escape", async () => {
     mockFetch.mockResolvedValueOnce({ ok: true, json: async () => [] });
     render(<FolderTree />);
-    const addBtn = screen.getByTitle("新建文件夹");
+    const addBtn = screen.getByTitle("New folder");
     await userEvent.click(addBtn);
-    const input = screen.getByPlaceholderText("文件夹名称");
+    const input = screen.getByPlaceholderText("Folder name");
     await userEvent.type(input, "test{escape}");
-    expect(screen.queryByPlaceholderText("文件夹名称")).not.toBeInTheDocument();
+    expect(screen.queryByPlaceholderText("Folder name")).not.toBeInTheDocument();
   });
 });

packages/frontend/app/home/cloud-docs/page.tsx

@@ -192,7 +192,7 @@ export default function CloudDocsPage() {
   };
 
   return (
-    <div className="min-h-screen bg-white flex w-full">
+    <div className="flex flex-1 w-full">
       {/* Folder tree sidebar */}
       <div className="flex-shrink-0">
         <FolderTree onDocClick={handleDocClick} />
@@ -243,7 +243,7 @@ export default function CloudDocsPage() {
                     : "text-gray-500 hover:text-gray-900"
                 }`}
               >
-                <span>与我共享</span>
+                <span>Shared with me</span>
               </button>
               <button
                 onClick={() => setActiveTab("favorites")}
@@ -253,7 +253,7 @@ export default function CloudDocsPage() {
                     : "text-gray-500 hover:text-gray-900"
                 }`}
               >
-                <span>收藏</span>
+                <span>Favorites</span>
               </button>
             </div>
           </div>
@@ -332,7 +332,7 @@ export default function CloudDocsPage() {
             </div>
           )}
 
-          {/* 创建文档 loading 遮罩 */}
+          {/** Document creation loading overlay */}
           {creatingDoc && (
             <div className="fixed inset-0 z-50 flex items-center justify-center bg-white/60 backdrop-blur-sm">
               <div className="flex flex-col items-center gap-3">

packages/frontend/app/home/knowledge-base/page.tsx

@@ -1,6 +1,6 @@
 "use client";
 import { useState } from "react";
-import { MdDatabase, MdAdd, MdSearch } from "react-icons/md";
+import { MdLibraryBooks, MdAdd, MdSearch } from "react-icons/md";
 
 const SAMPLE_ITEMS = [
   { id: 1, title: "Product Requirements 2024", updatedAt: "2 hours ago", count: 12 },
@@ -101,7 +101,7 @@ export default function KnowledgeBasePage() {
                   className="w-10 h-10 rounded-xl flex items-center justify-center"
                   style={{ background: "#f2f3ff" }}
                 >
-                  <MdDatabase size={20} style={{ color: "#0043b5" }} />
+                  <MdLibraryBooks size={20} style={{ color: "#0043b5" }} />
                 </div>
                 <div>
                   <p className="font-semibold text-sm" style={{ color: "#131b2e" }}>