Replace tuple return types with named records

CLAUDE.md prohibits tuples as return types. Add PagedResult<T>,
ProfileUpdateResult, and ApiKeyCreationResult records and update all
callers (AuditLogQueryService, AdminIdentityService, UserService,
ApiKeyService and their controllers/endpoints).

src/api/MicCheck.Api/Users/UserService.cs

@@ -9,23 +9,23 @@ public class UserService(IMicCheckDbContext db, IPasswordHasher<User> passwordHa
     public async Task<User?> FindByIdAsync(int userId, CancellationToken ct = default) =>
         await db.Users.FirstOrDefaultAsync(u => u.Id == userId && u.IsActive, ct);
 
-    public async Task<(User? User, bool EmailConflict)> UpdateProfileAsync(
+    public async Task<ProfileUpdateResult> UpdateProfileAsync(
         int userId, string firstName, string lastName, string email, CancellationToken ct = default)
     {
         var user = await db.Users.FirstOrDefaultAsync(u => u.Id == userId && u.IsActive, ct);
-        if (user is null) return (null, false);
+        if (user is null) return new ProfileUpdateResult(null, EmailConflict: false);
 
         if (!string.Equals(user.Email, email, StringComparison.OrdinalIgnoreCase))
         {
             var emailTaken = await db.Users.AnyAsync(u => u.Email == email && u.Id != userId, ct);
-            if (emailTaken) return (null, true);
+            if (emailTaken) return new ProfileUpdateResult(null, EmailConflict: true);
         }
 
         user.FirstName = firstName;
         user.LastName = lastName;
         user.Email = email;
         await db.SaveChangesAsync(ct);
-        return (user, false);
+        return new ProfileUpdateResult(user, EmailConflict: false);
     }
 
     public async Task<bool> ChangePasswordAsync(
@@ -42,3 +42,5 @@ public class UserService(IMicCheckDbContext db, IPasswordHasher<User> passwordHa
         return true;
     }
 }
+
+public record ProfileUpdateResult(User? User, bool EmailConflict);