feat: chat stop button, image paste, vision AI, search fixes

- Add stop button to all chat interfaces (floating, contextual, full-page)
- Add conversation sliding window (50 messages) to prevent context overflow
- Add chat timeout warning (30s toast)
- Force response language in chat system prompt (mandatory per-locale)
- Add image paste from clipboard in all note editors (card, list, input)
- Fix upload API to infer extension from MIME type for clipboard images
- Add image description support in note AI chat (base64 vision)
- Fix search regex crash on special characters (escape user input)
- Fix search case-insensitivity on PostgreSQL (mode: 'insensitive')
- Add try/catch around semantic search in chat route (prevent blocking)
- Add new chat button to floating AI assistant
- Fix empty thinking bubbles for reasoning models (filter non-text parts)
- Remove duplicate AI assistant toggle from note editor header
- Improve link metadata scraping (timeout, content-type check, relative URLs)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/components/note-editor.tsx

@@ -173,24 +173,23 @@ export function NoteEditor({ note, readOnly = false, onClose }: NoteEditorProps)
     return !dismissedTags.includes(s.tag) && !existingLabelsLower.includes(s.tag.toLowerCase())
   })
 
+  const uploadImageFile = async (file: File) => {
+    const formData = new FormData()
+    formData.append('file', file)
+    const response = await fetch('/api/upload', { method: 'POST', body: formData })
+    if (!response.ok) throw new Error('Upload failed')
+    const data = await response.json()
+    return data.url
+  }
+
   const handleImageUpload = async (e: React.ChangeEvent<HTMLInputElement>) => {
     const files = e.target.files
     if (!files) return
 
     for (const file of Array.from(files)) {
-      const formData = new FormData()
-      formData.append('file', file)
-
       try {
-        const response = await fetch('/api/upload', {
-          method: 'POST',
-          body: formData,
-        })
-
-        if (!response.ok) throw new Error('Upload failed')
-
-        const data = await response.json()
-        setImages(prev => [...prev, data.url])
+        const url = await uploadImageFile(file)
+        setImages(prev => [...prev, url])
       } catch (error) {
         console.error('Upload error:', error)
         toast.error(t('notes.uploadFailed', { filename: file.name }))
@@ -198,6 +197,29 @@ export function NoteEditor({ note, readOnly = false, onClose }: NoteEditorProps)
     }
   }
 
+  // Paste handler: upload clipboard images
+  useEffect(() => {
+    const handlePaste = async (e: ClipboardEvent) => {
+      const items = e.clipboardData?.items
+      if (!items) return
+      for (const item of Array.from(items)) {
+        if (item.type.startsWith('image/')) {
+          e.preventDefault()
+          const file = item.getAsFile()
+          if (!file) continue
+          try {
+            const url = await uploadImageFile(file)
+            setImages(prev => [...prev, url])
+          } catch {
+            toast.error(t('notes.uploadFailed', { filename: 'pasted image' }))
+          }
+        }
+      }
+    }
+    document.addEventListener('paste', handlePaste)
+    return () => document.removeEventListener('paste', handlePaste)
+  }, [t])
+
   const handleRemoveImage = (index: number) => {
     const removedUrl = images[index]
     setImages(images.filter((_, i) => i !== index))
@@ -597,21 +619,6 @@ export function NoteEditor({ note, readOnly = false, onClose }: NoteEditorProps)
               <div className="flex items-center justify-between">
                 <div className="flex items-center gap-2">
                   <h2 className="text-lg font-semibold">{readOnly ? t('notes.view') : t('notes.edit')}</h2>
-                  {/* AI Copilot Toggle Button next to title */}
-                  {note.type === 'text' && !readOnly && aiAssistantEnabled && (
-                    <Button
-                      variant="ghost" size="sm"
-                      className={cn(
-                        'h-8 gap-1.5 px-2 text-xs transition-colors ml-2',
-                        aiOpen && 'bg-primary/10 text-primary'
-                      )}
-                      onClick={() => setAiOpen(!aiOpen)}
-                      title="Toggle AI Copilot"
-                    >
-                      <Sparkles className="h-3.5 w-3.5" />
-                      <span className="hidden sm:inline">Assistant IA</span>
-                    </Button>
-                  )}
                 </div>
                 {readOnly && (
                   <Badge variant="secondary" className="bg-primary/10 text-primary dark:bg-primary/20 dark:text-primary-foreground">
@@ -978,6 +985,7 @@ export function NoteEditor({ note, readOnly = false, onClose }: NoteEditorProps)
             onClose={() => setAiOpen(false)}
             noteTitle={title}
             noteContent={content}
+            noteImages={images}
             onApplyToNote={(newContent) => {
               setPreviousContentForCopilot(content)
               setContent(newContent)