Add admin user management and improve UX

Features:
- Add user management for admins (CRUD operations)
- Add is_admin column to users table
- Add AdminMiddleware for authorization
- Add admin routes and views
- Add artisan command: user:set-admin

Improvements:
- Fix Quick Switcher: add x-data for Alpine.js dispatch
- Fix Quick Switcher: close on outside click
- Redirect non-admin users to front page after login
- Add Knowledge Base link in dashboard navigation
- Change app logo from Laravel to book icon

src/app/Console/Commands/SetUserAdmin.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Console\Commands;
+
+use App\Models\User;
+use Illuminate\Console\Command;
+
+class SetUserAdmin extends Command
+{
+    /**
+     * The name and signature of the console command.
+     *
+     * @var string
+     */
+    protected $signature = 'user:set-admin {email} {--remove : Remove admin status}';
+
+    /**
+     * The console command description.
+     *
+     * @var string
+     */
+    protected $description = 'Set or remove admin status for a user';
+
+    /**
+     * Execute the console command.
+     */
+    public function handle(): int
+    {
+        $email = $this->argument('email');
+        $user = User::where('email', $email)->first();
+
+        if (!$user) {
+            $this->error("User with email '{$email}' not found.");
+            return Command::FAILURE;
+        }
+
+        $isAdmin = !$this->option('remove');
+        $user->is_admin = $isAdmin;
+        $user->save();
+
+        if ($isAdmin) {
+            $this->info("User '{$user->name}' ({$email}) is now an admin.");
+        } else {
+            $this->info("Admin status removed from user '{$user->name}' ({$email}).");
+        }
+
+        return Command::SUCCESS;
+    }
+}
+

src/app/Http/Controllers/Admin/UserController.php

@@ -0,0 +1,104 @@
+<?php
+
+namespace App\Http\Controllers\Admin;
+
+use App\Http\Controllers\Controller;
+use App\Models\User;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Hash;
+use Illuminate\Validation\Rules;
+
+class UserController extends Controller
+{
+    /**
+     * Display a listing of the users.
+     */
+    public function index()
+    {
+        $users = User::orderBy('created_at', 'desc')->paginate(20);
+
+        return view('admin.users.index', compact('users'));
+    }
+
+    /**
+     * Show the form for creating a new user.
+     */
+    public function create()
+    {
+        return view('admin.users.create');
+    }
+
+    /**
+     * Store a newly created user in storage.
+     */
+    public function store(Request $request)
+    {
+        $validated = $request->validate([
+            'name' => ['required', 'string', 'max:255'],
+            'email' => ['required', 'string', 'lowercase', 'email', 'max:255', 'unique:users'],
+            'password' => ['required', 'confirmed', Rules\Password::defaults()],
+            'is_admin' => ['boolean'],
+        ]);
+
+        $user = User::create([
+            'name' => $validated['name'],
+            'email' => $validated['email'],
+            'password' => Hash::make($validated['password']),
+            'is_admin' => $request->boolean('is_admin'),
+        ]);
+
+        return redirect()->route('admin.users.index')
+            ->with('success', 'ユーザーを作成しました。');
+    }
+
+    /**
+     * Show the form for editing the specified user.
+     */
+    public function edit(User $user)
+    {
+        return view('admin.users.edit', compact('user'));
+    }
+
+    /**
+     * Update the specified user in storage.
+     */
+    public function update(Request $request, User $user)
+    {
+        $validated = $request->validate([
+            'name' => ['required', 'string', 'max:255'],
+            'email' => ['required', 'string', 'lowercase', 'email', 'max:255', 'unique:users,email,' . $user->id],
+            'password' => ['nullable', 'confirmed', Rules\Password::defaults()],
+            'is_admin' => ['boolean'],
+        ]);
+
+        $user->name = $validated['name'];
+        $user->email = $validated['email'];
+        $user->is_admin = $request->boolean('is_admin');
+
+        if (!empty($validated['password'])) {
+            $user->password = Hash::make($validated['password']);
+        }
+
+        $user->save();
+
+        return redirect()->route('admin.users.index')
+            ->with('success', 'ユーザー情報を更新しました。');
+    }
+
+    /**
+     * Remove the specified user from storage.
+     */
+    public function destroy(User $user)
+    {
+        // 自分自身は削除できない
+        if ($user->id === auth()->id()) {
+            return back()->with('error', '自分自身を削除することはできません。');
+        }
+
+        $user->delete();
+
+        return redirect()->route('admin.users.index')
+            ->with('success', 'ユーザーを削除しました。');
+    }
+}
+

src/app/Http/Controllers/Auth/AuthenticatedSessionController.php

@@ -28,7 +28,12 @@ public function store(LoginRequest $request): RedirectResponse
 
         $request->session()->regenerate();
 
-        return redirect()->intended(route('dashboard', absolute: false));
+        // 管理者はダッシュボードへ、一般ユーザーはフロントページへリダイレクト
+        if (Auth::user()->isAdmin()) {
+            return redirect()->intended(route('dashboard', absolute: false));
+        }
+
+        return redirect()->intended('/');
     }
 
     /**

src/app/Http/Middleware/AdminMiddleware.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+class AdminMiddleware
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Closure(\Illuminate\Http\Request): (\Symfony\Component\HttpFoundation\Response)  $next
+     */
+    public function handle(Request $request, Closure $next): Response
+    {
+        if (!$request->user() || !$request->user()->isAdmin()) {
+            abort(403, 'Unauthorized. Admin access required.');
+        }
+
+        return $next($request);
+    }
+}
+

src/app/Models/User.php

@@ -21,8 +21,19 @@ class User extends Authenticatable
         'name',
         'email',
         'password',
+        'is_admin',
     ];
 
+    /**
+     * Check if user is an administrator.
+     *
+     * @return bool
+     */
+    public function isAdmin(): bool
+    {
+        return (bool) $this->is_admin;
+    }
+
     /**
      * The attributes that should be hidden for serialization.
      *