Add membership fee system with disability discount and fix document permissions

Features:
- Implement two fee types: entrance fee and annual fee (both NT$1,000)
- Add 50% discount for disability certificate holders
- Add disability certificate upload in member profile
- Integrate disability verification into cashier approval workflow
- Add membership fee settings in system admin

Document permissions:
- Fix hard-coded role logic in Document model
- Use permission-based authorization instead of role checks

Additional features:
- Add announcements, general ledger, and trial balance modules
- Add income management and accounting entries
- Add comprehensive test suite with factories
- Update UI translations to Traditional Chinese

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/Models/User.php

@@ -23,7 +23,6 @@ class User extends Authenticatable
     protected $fillable = [
         'name',
         'email',
-        'is_admin',
         'profile_photo_path',
         'password',
     ];
@@ -46,7 +45,6 @@ class User extends Authenticatable
     protected $casts = [
         'email_verified_at' => 'datetime',
         'password' => 'hashed',
-        'is_admin' => 'boolean',
     ];
 
     public function member(): HasOne
@@ -54,6 +52,15 @@ class User extends Authenticatable
         return $this->hasOne(Member::class);
     }
 
+    /**
+     * 檢查使用者是否為管理員
+     * 使用 Spatie Permission 的 admin 角色取代舊版 is_admin 欄位
+     */
+    public function isAdmin(): bool
+    {
+        return $this->hasRole('admin');
+    }
+
     public function profilePhotoUrl(): ?string
     {
         if (! $this->profile_photo_path) {