refactor(system): rename Threat Intel Scan to Security Feed Monitor

The previous name implied data from a dedicated threat intelligence team.
The feature actually monitors public RSS feeds and security blogs for
ATT&CK technique mentions, so Security Feed Monitor is more accurate.
Updated description and all references across SystemPage and ReviewQueuePage.

frontend/src/pages/ReviewQueuePage.tsx

@@ -421,7 +421,7 @@ export default function ReviewQueuePage() {
           </p>
           <ul className="ml-4 list-disc space-y-1 text-xs text-amber-400/80">
             <li>The MITRE ATT&CK sync detected an update to the technique</li>
-            <li>The Threat Intel Scan found a new article about this technique in a security feed</li>
+            <li>The Security Feed Monitor found a new article about this technique in a public security feed</li>
             <li>A new detection rule or test template was added for this technique</li>
           </ul>
           <p className="text-xs text-amber-400/70">

frontend/src/pages/SystemPage.tsx

@@ -236,9 +236,9 @@ export default function SystemPage() {
               <Search className="h-6 w-6 text-purple-400" />
             </div>
             <div className="flex-1">
-              <h2 className="text-lg font-semibold text-white">Threat Intel Scan</h2>
+              <h2 className="text-lg font-semibold text-white">Security Feed Monitor</h2>
               <p className="mt-1 text-sm text-gray-400">
-                Scan RSS feeds and security blogs for new threat intelligence related to techniques.
+                Monitor public RSS feeds and security blogs for new articles and research related to MITRE ATT&CK techniques.
               </p>
 
               {schedulerStatus && (