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/note-editor/index.tsx

@@ -0,0 +1,37 @@
+'use client'
+
+import { NoteEditorProvider, useNoteEditorContext } from './note-editor-context'
+import { NoteEditorFullPage } from './note-editor-full-page'
+import { NoteEditorDialog } from './note-editor-dialog'
+import { Note } from '@/lib/types'
+
+interface NoteEditorProps {
+  note: Note
+  readOnly?: boolean
+  onClose: () => void
+  fullPage?: boolean
+}
+
+export function NoteEditor({ note, readOnly, onClose, fullPage = false }: NoteEditorProps) {
+  return (
+    <NoteEditorProvider note={note} readOnly={readOnly} fullPage={fullPage}>
+      {fullPage ? (
+        <NoteEditorFullPage onClose={onClose} />
+      ) : (
+        <NoteEditorDialog onClose={onClose} />
+      )}
+    </NoteEditorProvider>
+  )
+}
+
+// Re-export context hook for backwards compatibility
+export { useNoteEditorContext } from './note-editor-context'
+
+// Re-export sub-components for advanced usage
+export { NoteEditorFullPage } from './note-editor-full-page'
+export { NoteEditorDialog } from './note-editor-dialog'
+export { NoteEditorProvider } from './note-editor-context'
+export { NoteTitleBlock } from './note-title-block'
+export { NoteContentArea } from './note-content-area'
+export { NoteMetadataSection } from './note-metadata-section'
+export { NoteEditorToolbar } from './note-editor-toolbar'