fix: restore watermark image in email templates

The previous commit incorrectly removed the watermark — only the
style extraction into <style> blocks was requested. Restores the
watermark <img>, {{watermarkUrl}} placeholder resolution in both
EmailConnectorService and PasswordResetNotificationService, and
the corresponding test assertions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/resources/email-templates/password-reset-notification.html

@@ -10,7 +10,9 @@
     .wrapper { font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif; max-width:480px; margin:0 auto; background:#fff; border-radius:8px; overflow:hidden; border:1px solid #e8e0d4; }
     .header { background:#C6820E; padding:20px 24px; text-align:center; }
     .header span { font-size:22px; font-weight:700; color:#fff; letter-spacing:0.5px; }
-    .content { padding:32px 24px 24px; }
+    .content { padding:32px 24px 24px; position:relative; overflow:hidden; }
+    .watermark { position:absolute; top:-30px; right:-50px; width:320px; height:320px; opacity:0.07; pointer-events:none; border:0; outline:none; }
+    .inner { position:relative; }
     .title { color:#1a1a1a; font-size:16px; font-weight:600; margin:0 0 8px; }
     .subtitle { color:#444; font-size:14px; line-height:1.6; margin:0 0 16px; }
     .mfa-note { background:#FDF6EC; border:1px solid #e8e0d4; border-radius:6px; padding:12px 16px; margin:0 0 16px; }
@@ -29,6 +31,8 @@
       <span>Cameleer.io</span>
     </div>
     <div class="content">
+      <img src="{{watermarkUrl}}" class="watermark" alt="" />
+      <div class="inner">
       <p class="title">Your password was reset</p>
       <p class="subtitle">Your Cameleer account password was successfully changed on {{timestamp}}.</p>
       <div class="mfa-note">
@@ -36,6 +40,7 @@
       </div>
       <p class="hint">If this wasn't you, contact your administrator immediately.</p>
       <p class="detail">This is an automated security notification from your Cameleer account. Cameleer is an observability platform for Apache Camel integrations providing real-time route tracing, message inspection, and performance monitoring. You are receiving this notification because a password change was completed. For your security, we recommend reviewing your account activity and ensuring your credentials are kept safe.</p>
+      </div>
     </div>
     <div class="footer">
       <p class="contact">Questions? Contact your administrator</p>