feat: Add multi-language support (i18n)

Languages supported (8):
- English (en)
- 日本語 (ja)
- Deutsch (de)
- Français (fr)
- Español (es)
- 简体中文 (zh-CN)
- 繁體中文 (zh-TW)
- 한국어 (ko)

Changes:
- Add locale column to users table
- Add SetLocale middleware for automatic locale detection
- Add LocaleController for language switching
- Create language files with translations for all UI elements
- Add language selector to user profile page
- Update all Blade views to use translation strings

src/bootstrap/app.php

@@ -14,6 +14,11 @@
         $middleware->alias([
             'admin' => \App\Http\Middleware\AdminMiddleware::class,
         ]);
+        
+        // Add SetLocale middleware to web group
+        $middleware->web(append: [
+            \App\Http\Middleware\SetLocale::class,
+        ]);
     })
     ->withExceptions(function (Exceptions $exceptions): void {
         //