Add SMTP support for Authelia notifications and fix config persistence

SMTP: Add host, port, username, sender, and password fields to the
Authelia configuration. Uses modern address format (submission:// for
STARTTLS on 587, smtps:// for implicit TLS on 465) with explicit TLS
server name. Falls back to filesystem notifier when SMTP is not
configured.

Fixes: Config changes now persist before attempting service restart,
so a restart failure (e.g. bad SMTP credentials) no longer prevents
saving. The specific Authelia error is extracted from the journal and
shown in the UI.

Frontend: SMTP fields added to the Authentication config card. Form
no longer continuously resets from server state while user is editing.
OIDC client edit UI added (pencil icon).

web/src/hooks/useAuthelia.ts

@@ -29,7 +29,7 @@ export function useAuthelia() {
   };
 
   const updateConfigMutation = useMutation({
-    mutationFn: (data: { enabled?: boolean; domain?: string; defaultPolicy?: string }) =>
+    mutationFn: (data: { enabled?: boolean; domain?: string; defaultPolicy?: string; smtpHost?: string; smtpPort?: number; smtpUsername?: string; smtpSender?: string; smtpPassword?: string }) =>
       autheliaApi.updateConfig(data),
     onSuccess: invalidateAll,
   });