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/resources/views/profile/edit.blade.php

@@ -13,6 +13,12 @@
                 </div>
             </div>
 
+            <div class="p-4 sm:p-8 bg-white shadow sm:rounded-lg">
+                <div class="max-w-xl">
+                    @include('profile.partials.update-locale-form')
+                </div>
+            </div>
+
             <div class="p-4 sm:p-8 bg-white shadow sm:rounded-lg">
                 <div class="max-w-xl">
                     @include('profile.partials.update-password-form')