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/forgot-password.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 24px; }
     .code-box { text-align:center; margin:0 0 24px; }
@@ -30,6 +32,8 @@
       <span>Cameleer.io</span>
     </div>
     <div class="content">
+      <img src="{{watermarkUrl}}" class="watermark" alt="" />
+      <div class="inner">
       <p class="title">Lost in the dunes?</p>
       <p class="subtitle">No worries — enter this code to reset your password and get back on the trail.</p>
       <div class="code-box">
@@ -39,6 +43,7 @@
       </div>
       <p class="hint">This code expires in 10 minutes. If you didn't request a password reset, you can safely ignore this email.</p>
       <p class="detail">This password reset was requested for your Cameleer account. Cameleer is an observability platform for Apache Camel integrations providing real-time route tracing, message inspection, and performance monitoring. For security, this code can only be used once. If you continue to have trouble accessing your account, please contact your administrator for assistance.</p>
+      </div>
     </div>
     <div class="footer">
       <p class="contact">Questions? Contact your administrator</p>