improvement: make phone number input more flexible with auto-formatting

- Accept phone numbers with or without hyphens/spaces (01012345678, 010-1234-5678, etc)
- Auto-format to standard 010-XXXX-XXXX or 010-XXXX-XXXXX format on backend
- Remove strict regex validation that forced user input format
- Better UX: accept user input as-is and normalize in backend

Closes issue with phone number validation being too strict.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/TaxBaik.Application/Services/InquiryService.cs

@@ -12,7 +12,7 @@ public class InquiryService(
     IInquiryNotificationService notificationService,
     IMemoryCache memoryCache)
 {
-    private static readonly Regex PhoneRegex = new(@"^01[0-9]-\d{3,4}-\d{4}$");
+    private static readonly Regex PhoneRegex = new(@"^01[0-9]\d{7,8}$");
 
     public async Task<int> SubmitAsync(
         string name, string phone, string serviceType, string message,
@@ -21,8 +21,11 @@ public class InquiryService(
         if (string.IsNullOrWhiteSpace(name))
             throw new ValidationException("이름을 입력하세요.");
 
-        if (!PhoneRegex.IsMatch(phone))
-            throw new ValidationException("올바른 전화번호를 입력하세요. (예: 010-1234-5678)");
+        var cleanPhone = phone?.Replace("-", "").Replace(" ", "").Trim() ?? "";
+        if (!PhoneRegex.IsMatch(cleanPhone) || cleanPhone.Length < 10)
+            throw new ValidationException("올바른 전화번호를 입력하세요. (예: 01012345678 또는 010-1234-5678)");
+
+        var formattedPhone = FormatPhoneNumber(cleanPhone);
 
         if (string.IsNullOrWhiteSpace(message))
             throw new ValidationException("문의 내용을 입력하세요.");
@@ -30,7 +33,7 @@ public class InquiryService(
         var inquiry = new Inquiry
         {
             Name = name.Trim(),
-            Phone = phone.Trim(),
+            Phone = formattedPhone,
             Email = string.IsNullOrWhiteSpace(email) ? null : email.Trim(),
             ServiceType = serviceType ?? "기타",
             Message = message.Trim(),
@@ -82,8 +85,9 @@ public class InquiryService(
         if (string.IsNullOrWhiteSpace(dto.Name))
             throw new ValidationException("이름을 입력하세요.");
 
-        if (!PhoneRegex.IsMatch(dto.Phone))
-            throw new ValidationException("올바른 전화번호를 입력하세요. (예: 010-1234-5678)");
+        var cleanPhone = dto.Phone?.Replace("-", "").Replace(" ", "").Trim() ?? "";
+        if (!PhoneRegex.IsMatch(cleanPhone) || cleanPhone.Length < 10)
+            throw new ValidationException("올바른 전화번호를 입력하세요. (예: 01012345678 또는 010-1234-5678)");
 
         if (string.IsNullOrWhiteSpace(dto.Message))
             throw new ValidationException("문의 내용을 입력하세요.");
@@ -92,7 +96,7 @@ public class InquiryService(
             throw new ValidationException("지원하지 않는 문의 상태입니다.");
 
         inquiry.Name = dto.Name.Trim();
-        inquiry.Phone = dto.Phone.Trim();
+        inquiry.Phone = FormatPhoneNumber(cleanPhone);
         inquiry.Email = string.IsNullOrWhiteSpace(dto.Email) ? null : dto.Email.Trim();
         inquiry.ServiceType = string.IsNullOrWhiteSpace(dto.ServiceType) ? "기타" : dto.ServiceType.Trim();
         inquiry.Message = dto.Message.Trim();
@@ -144,6 +148,23 @@ public class InquiryService(
 
         return InquiryStatusMapper.ToStorageValue(parsed);
     }
+
+    private static string FormatPhoneNumber(string phone)
+    {
+        if (string.IsNullOrWhiteSpace(phone))
+            return phone ?? "";
+
+        var clean = phone.Replace("-", "").Replace(" ", "").Trim();
+        if (clean.Length < 10 || clean.Length > 11)
+            return clean;
+
+        return clean.Length switch
+        {
+            10 => $"{clean[..3]}-{clean[3..6]}-{clean[6..]}",  // 01012345678 → 010-123-45678
+            11 => $"{clean[..3]}-{clean[3..7]}-{clean[7..]}",  // 010123456789 → 010-1234-56789
+            _ => clean
+        };
+    }
 }
 
 public class ValidationException : Exception