気象データ画面を追加（月別サマリー・直近14日）

- /weather ページ: 月別集計テーブル・年間サマリーカード・直近14日日次記録
- Navbar に「気象」リンク追加

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/Navbar.tsx

@@ -1,7 +1,7 @@
 'use client';
 
 import { useRouter, usePathname } from 'next/navigation';
-import { LogOut, Wheat, MapPin, FileText, Upload, LayoutDashboard, Mail, History, Shield, KeyRound } from 'lucide-react';
+import { LogOut, Wheat, MapPin, FileText, Upload, LayoutDashboard, Mail, History, Shield, KeyRound, Cloud } from 'lucide-react';
 import { logout } from '@/lib/api';
 
 export default function Navbar() {
@@ -100,6 +100,17 @@ export default function Navbar() {
                 <Shield className="h-4 w-4 mr-2" />
                 メールルール
               </button>
+              <button
+                onClick={() => router.push('/weather')}
+                className={`flex items-center px-3 py-2 text-sm rounded-md transition-colors ${
+                  isActive('/weather')
+                    ? 'text-green-700 bg-green-50'
+                    : 'text-gray-700 hover:text-gray-900 hover:bg-gray-100'
+                }`}
+              >
+                <Cloud className="h-4 w-4 mr-2" />
+                気象
+              </button>
             </div>
           </div>
           <div className="flex items-center space-x-1">