Refactor EmailAccountDto and improve encryption logic

Refactored `EmailAccountDto` to focus on SMTP-related properties, removing unused fields. Updated `DependencyInjection` to configure data protection with a new key storage path. Simplified `DataProtectionEncryptionService` by removing redundant checks and error handling for encryption and decryption methods.

src/DigitalData.EmailProfiler.Infrastructure/Services/DataProtectionEncryptionService.cs

@@ -13,25 +13,11 @@ public class DataProtectionEncryptionService(IDataProtectionProvider Provider) :
 
     public string Encrypt(string plainText)
     {
-        if (string.IsNullOrEmpty(plainText))
-            return string.Empty;
-
         return Protector.Protect(plainText);
     }
 
     public string Decrypt(string cipherText)
     {
-        if (string.IsNullOrEmpty(cipherText))
-            return string.Empty;
-
-        try
-        {
-            return Protector.Unprotect(cipherText);
-        }
-        catch (Exception)
-        {
-            // If decryption fails, return empty (corrupt data or wrong key)
-            return string.Empty;
-        }
+        return Protector.Unprotect(cipherText);
     }
 }