fix(memory-echo): fix fusion route config and single close button on comparison modal

- Fix fusion route using same broken prisma.systemConfig.findFirst()
  instead of getSystemConfig() — this caused all fusion requests to fail
- Replace duplicate close buttons (Radix auto + custom) with single
  styled close button in comparison modal header

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

keep-notes/components/comparison-modal.tsx

@@ -3,7 +3,7 @@
 import { useState } from 'react'
 import { Dialog, DialogContent } from '@/components/ui/dialog'
 import { Button } from '@/components/ui/button'
-import { Sparkles, ThumbsUp, ThumbsDown, GitMerge } from 'lucide-react'
+import { Sparkles, ThumbsUp, ThumbsDown, GitMerge, X } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { Note } from '@/lib/types'
 import { useLanguage } from '@/lib/i18n/LanguageProvider'
@@ -70,10 +70,13 @@ export function ComparisonModal({
 
   return (
     <Dialog open={isOpen} onOpenChange={onClose}>
-      <DialogContent className={cn(
-        "max-h-[90vh] overflow-hidden flex flex-col p-0",
-        maxModalWidth
-      )}>
+      <DialogContent
+        showCloseButton={false}
+        className={cn(
+          "max-h-[90vh] overflow-hidden flex flex-col p-0",
+          maxModalWidth
+        )}
+      >
         {/* Header */}
         <div className="flex items-center justify-between p-6 border-b dark:border-zinc-700">
           <div className="flex items-center gap-3">
@@ -89,6 +92,12 @@ export function ComparisonModal({
               </p>
             </div>
           </div>
+          <button
+            onClick={onClose}
+            className="p-1 rounded-md text-gray-500 hover:text-gray-700 dark:hover:text-gray-300 hover:bg-gray-100 dark:hover:bg-zinc-800 transition-colors"
+          >
+            <X className="h-5 w-5" />
+          </button>
         </div>
 
         {/* AI Insight Section */}