refactor: 移除主题切换功能，统一使用明亮风格

- 从 Header 移除 ThemeToggle 组件
- 删除 theme-toggle.tsx 文件
- 简化 theme-context.tsx，只保留 light 主题~

src/components/layout/header.tsx

@@ -4,7 +4,6 @@ import { useState, useEffect, useCallback } from 'react';
 import { Menu, X } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
 import { Button } from '@/components/ui/button';
-import { ThemeToggle } from '@/components/ui/theme-toggle';
 import { COMPANY_INFO, NAVIGATION } from '@/lib/constants';
 
 export function Header() {
@@ -64,7 +63,7 @@ export function Header() {
           fixed top-0 left-0 right-0 z-50
           transition-all duration-300 ease-out
           ${isScrolled 
-            ? 'bg-[var(--color-bg-primary)]/80 backdrop-blur-xl border-b border-[var(--color-border-primary)] shadow-[0_4px_30px_rgba(0,217,255,0.1)]' 
+            ? 'bg-white/95 backdrop-blur-xl border-b border-[#E2E8F0] shadow-sm' 
             : 'bg-transparent'
           }
         `}
@@ -93,8 +92,8 @@ export function Header() {
                     relative px-3 py-1.5 text-sm font-medium
                     transition-all duration-300
                     ${activeSection === item.id.replace('#', '')
-                      ? 'text-[var(--color-tech-blue)]'
-                      : 'text-[var(--color-text-secondary)] hover:text-[var(--color-tech-blue)]'
+                      ? 'text-[#005EB8]'
+                      : 'text-[#4A5568] hover:text-[#005EB8]'
                     }
                   `}
                 >
@@ -102,7 +101,7 @@ export function Header() {
                   {activeSection === item.id.replace('#', '') && (
                     <motion.span 
                       layoutId="activeNav"
-                      className="absolute bottom-0 left-1/2 -translate-x-1/2 w-6 h-0.5 bg-gradient-to-r from-[var(--color-tech-blue)] to-[var(--color-tech-purple)] rounded-full"
+                      className="absolute bottom-0 left-1/2 -translate-x-1/2 w-6 h-0.5 bg-[#005EB8] rounded-full"
                       transition={{ type: "spring", stiffness: 380, damping: 30 }}
                     />
                   )}
@@ -111,7 +110,6 @@ export function Header() {
             </nav>
 
             <div className="hidden md:flex items-center gap-3">
-              <ThemeToggle />
               <Button 
                 variant="ghost"
                 size="sm"
@@ -138,7 +136,7 @@ export function Header() {
             </div>
 
             <button
-              className="md:hidden p-2 -mr-2 text-[var(--color-text-secondary)] hover:text-[var(--color-tech-blue)] transition-colors"
+              className="md:hidden p-2 -mr-2 text-[#4A5568] hover:text-[#005EB8] transition-colors"
               onClick={() => setIsOpen(!isOpen)}
             >
               {isOpen ? <X className="w-5 h-5" /> : <Menu className="w-5 h-5" />}
@@ -156,7 +154,7 @@ export function Header() {
             className="fixed inset-0 z-40 md:hidden"
           >
             <div 
-              className="absolute inset-0 bg-black/60 backdrop-blur-sm"
+              className="absolute inset-0 bg-black/20 backdrop-blur-sm"
               onClick={() => setIsOpen(false)}
             />
             <motion.div 
@@ -164,7 +162,7 @@ export function Header() {
               animate={{ y: 0, opacity: 1 }}
               exit={{ y: -20, opacity: 0 }}
               transition={{ type: "spring", stiffness: 300, damping: 30 }}
-              className="absolute top-16 left-0 right-0 bg-[var(--color-bg-secondary)]/95 backdrop-blur-xl border-b border-[var(--color-border-primary)] shadow-[0_4px_30px_rgba(0,217,255,0.1)]"
+              className="absolute top-16 left-0 right-0 bg-white/95 backdrop-blur-xl border-b border-[#E2E8F0] shadow-lg"
             >
               <nav className="container-wide py-4">
                 {NAVIGATION.map((item, index) => (
@@ -180,19 +178,15 @@ export function Header() {
                       transition-all duration-300
                       border-l-2
                       ${activeSection === item.id.replace('#', '')
-                        ? 'text-[var(--color-tech-blue)] border-[var(--color-tech-blue)] bg-[rgba(0,217,255,0.1)]'
-                        : 'text-[var(--color-text-secondary)] border-transparent hover:text-[var(--color-tech-blue)] hover:bg-[rgba(255,255,255,0.05)]'
+                        ? 'text-[#005EB8] border-[#005EB8] bg-[#E8F4FD]'
+                        : 'text-[#4A5568] border-transparent hover:text-[#005EB8] hover:bg-[#F5F7FA]'
                       }
                     `}
                   >
                     {item.label}
                   </motion.a>
                 ))}
-                <div className="mt-4 px-4 pt-4 border-t border-[var(--color-border-primary)] space-y-3">
-                  <div className="flex items-center justify-between">
-                    <span className="text-sm text-[var(--color-text-tertiary)]">主题模式</span>
-                    <ThemeToggle />
-                  </div>
+                <div className="mt-4 px-4 pt-4 border-t border-[#E2E8F0] space-y-3">
                   <Button 
                     className="w-full"
                     onClick={() => {