fix: add sender_email to UserSmtpConfig to fix SMTP From header (501 bad sender address)

Agent-Logs-Url: https://github.com/christianlouis/InboxConverge/sessions/dc853384-976a-46e5-945b-60c9a9cce638

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/src/lib/api.ts

@@ -224,6 +224,7 @@ export interface UserSmtpConfig {
   host: string;
   port: number;
   username: string;
+  sender_email: string;
   use_tls: boolean;
   has_password: boolean;
   created_at: string;
@@ -485,6 +486,7 @@ export const smtpApi = {
     host: string;
     port: number;
     username: string;
+    sender_email: string;
     password?: string;
     use_tls: boolean;
   }): Promise<UserSmtpConfig> {