feat(email): generic webhook for all notification emails, hide SMTP UI

- Renamed the password-setup webhook (email_webhook.*, /system/email-webhook-config)
  and made it the single transport for all notification emails.
- New webhook_email_service.py shared by password_setup_service and
  notification_service.
- Wired test validated/rejected, campaign completed, and new-MITRE-technique
  notifications through the webhook (previously dead SMTP code, never triggered).
- Added POST /system/email-webhook-test to send a real test email.
- Hid the Email/SMTP settings tab from the UI (SMTP code kept intact, unused).
- Redact email_webhook.api_key on config export.

frontend/src/api/settings.ts

@@ -199,29 +199,34 @@ export async function testJiraConnection(): Promise<{
   return data;
 }
 
-export interface PasswordWebhookConfigOut {
+export interface EmailWebhookConfigOut {
   configured: boolean;
   url: string;
   api_key_set: boolean;
 }
 
-export async function getPasswordWebhookConfig(): Promise<PasswordWebhookConfigOut> {
-  const { data } = await client.get<PasswordWebhookConfigOut>("/system/password-webhook-config");
+export async function getEmailWebhookConfig(): Promise<EmailWebhookConfigOut> {
+  const { data } = await client.get<EmailWebhookConfigOut>("/system/email-webhook-config");
   return data;
 }
 
 /** apiKey is optional — omit or pass "" to leave the currently-stored key unchanged. */
-export async function updatePasswordWebhookConfig(
+export async function updateEmailWebhookConfig(
   url: string,
   apiKey?: string,
-): Promise<PasswordWebhookConfigOut> {
-  const { data } = await client.patch<PasswordWebhookConfigOut>("/system/password-webhook-config", {
+): Promise<EmailWebhookConfigOut> {
+  const { data } = await client.patch<EmailWebhookConfigOut>("/system/email-webhook-config", {
     url,
     api_key: apiKey || undefined,
   });
   return data;
 }
 
+export async function testEmailWebhook(to: string): Promise<{ detail: string }> {
+  const { data } = await client.post<{ detail: string }>("/system/email-webhook-test", { to });
+  return data;
+}
+
 export async function testTempoConnection(): Promise<{
   status: "ok" | "error" | "disabled";
   message?: string;