refactor: split NoteEditor into focused components + consolidate contexts

Phase 1: NoteEditor Split (64KB → 9 focused components)
- components/note-editor/: types.ts, context, toolbar, title-block,
  content-area, metadata-section, full-page, dialog compositions
- Maintains backwards compatibility via re-export from note-editor.tsx

Phase 2: Context Consolidation (5 → 3 contexts)
- NotebooksContext absorbs LabelContext (labels CRUD)
- EditorUIContext merges HomeViewContext + NotebookDragContext
- Removed: LabelContext, home-view-context, notebook-drag-context

Phase 3: React Query Infrastructure
- Added QueryProvider with @tanstack/react-query
- lib/query-keys.ts: centralized query key definitions
- lib/query-hooks.ts: useNotes, useNotebooksQuery, useLabelsQuery
- lib/use-refresh.ts: hybrid invalidateQueries + triggerRefresh helper
- NotebooksContext: invalidateQueries on mutations (with triggerRefresh fallback)

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

memento-note/components/masonry-grid.tsx

@@ -22,7 +22,7 @@ import { CSS } from '@dnd-kit/utilities';
 import { Note } from '@/lib/types';
 import { NoteCard } from './note-card';
 import { updateFullOrderWithoutRevalidation } from '@/app/actions/notes';
-import { useNotebookDrag } from '@/context/notebook-drag-context';
+import { useEditorUI } from '@/context/editor-ui-context';
 import { useLanguage } from '@/lib/i18n';
 import { useCardSizeMode } from '@/hooks/use-card-size-mode';
 import dynamic from 'next/dynamic';
@@ -175,7 +175,7 @@ export function MasonryGrid({
 }: MasonryGridProps) {
   const { t } = useLanguage();
   const [editingNote, setEditingNote] = useState<{ note: Note; readOnly?: boolean } | null>(null);
-  const { startDrag, endDrag, draggedNoteId } = useNotebookDrag();
+  const { startDrag, endDrag, draggedNoteId } = useEditorUI();
   const cardSizeMode = useCardSizeMode();
   const isUniformMode = cardSizeMode === 'uniform';