feat: 8 AI providers, rich text editor, agent notifications, UI contrast & font settings

- Add DeepSeek, OpenRouter, Mistral, Z.AI, LM Studio as AI providers
  with editable model names via Combobox in admin settings
- Fix OpenRouter broken by normalizeProvider bug in config.ts
- Convert agent-created notes from Markdown to HTML (TipTap rich text)
- Add Notification model + in-app notifications for agent results
- Agent notification click opens the created note directly
- Add note count display on notebook and inbox headers
- Fix checklist toggle in card view (persist state via localCheckItems)
- Add checklist creation option in tabs/list view (dropdown on + button)
- Fix image description ENOENT error with HTTP fallback
- Improve UI contrast across all themes (input, border, checkbox visibility)
- Add font family setting (Inter vs System Default) in Appearance settings
- Fix CSS font-sans variable conflict (removed dead Geist references)
- Update README with new features and 8 providers

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

memento-note/components/note-card.tsx

@@ -218,6 +218,13 @@ export const NoteCard = memo(function NoteCard({
 
   // Local color state so color persists after transition ends
   const [localColor, setLocalColor] = useState(note.color)
+  // Local checkItems state so checklist toggles persist after transition ends
+  const [localCheckItems, setLocalCheckItems] = useState(note.checkItems)
+
+  // Sync local state when parent data refreshes
+  useEffect(() => {
+    setLocalCheckItems(note.checkItems)
+  }, [note.checkItems])
 
   const colorClasses = NOTE_COLORS[(localColor || optimisticNote.color) as NoteColor] || NOTE_COLORS.default
 
@@ -373,14 +380,15 @@ export const NoteCard = memo(function NoteCard({
   }
 
   const handleCheckItem = async (checkItemId: string) => {
-    if (note.type === 'checklist' && Array.isArray(note.checkItems)) {
-      const updatedItems = note.checkItems.map(item =>
+    if (note.type === 'checklist') {
+      const currentItems = localCheckItems || note.checkItems || []
+      const updatedItems = currentItems.map(item =>
         item.id === checkItemId ? { ...item, checked: !item.checked } : item
       )
+      setLocalCheckItems(updatedItems) // instant visual update, survives transition
       startTransition(async () => {
         addOptimisticNote({ checkItems: updatedItems })
         await updateNote(note.id, { checkItems: updatedItems })
-        // No router.refresh() — optimistic update is sufficient and avoids grid rebuild
       })
     }
   }
@@ -621,7 +629,7 @@ export const NoteCard = memo(function NoteCard({
       {/* Content */}
       {optimisticNote.type === 'checklist' ? (
         <NoteChecklist
-          items={optimisticNote.checkItems || []}
+          items={localCheckItems || optimisticNote.checkItems || []}
           onToggleItem={handleCheckItem}
         />
       ) : optimisticNote.type === 'richtext' ? (