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/package.json

@@ -25,6 +25,7 @@
     "test:migration:watch": "vitest watch tests/migration"
   },
   "dependencies": {
+    "@ai-sdk/anthropic": "^3.0.76",
     "@ai-sdk/openai": "^3.0.7",
     "@ai-sdk/react": "^3.0.170",
     "@auth/prisma-adapter": "^2.11.1",
@@ -45,6 +46,7 @@
     "@radix-ui/react-slot": "^1.2.4",
     "@radix-ui/react-switch": "^1.2.6",
     "@radix-ui/react-tooltip": "^1.2.8",
+    "@tanstack/react-query": "^5.100.9",
     "@tiptap/extension-color": "^3.22.5",
     "@tiptap/extension-highlight": "^3.22.5",
     "@tiptap/extension-image": "^3.22.5",