chore: clean up repo for public release

- Remove BMAD framework, IDE configs, dev screenshots, test files,
  internal docs, and backup files
- Rename keep-notes/ to memento-note/
- Update all references from keep-notes to memento-note
- Add Apache 2.0 license with Commons Clause (non-commercial restriction)
- Add clean .gitignore and .env.docker.example

memento-note/context/notebook-drag-context.tsx

@@ -0,0 +1,64 @@
+'use client'
+
+import { createContext, useContext, useState, useCallback, ReactNode } from 'react'
+
+interface NotebookDragContextValue {
+  draggedNoteId: string | null
+  dragOverNotebookId: string | null
+  startDrag: (noteId: string) => void
+  endDrag: () => void
+  dragOver: (notebookId: string | null) => void
+  isDragging: boolean
+  isDragOver: boolean
+}
+
+const NotebookDragContext = createContext<NotebookDragContextValue | null>(null)
+
+export function useNotebookDrag() {
+  const context = useContext(NotebookDragContext)
+  if (!context) {
+    throw new Error('useNotebookDrag must be used within NotebookDragProvider')
+  }
+  return context
+}
+
+interface NotebookDragProviderProps {
+  children: ReactNode
+}
+
+export function NotebookDragProvider({ children }: NotebookDragProviderProps) {
+  const [draggedNoteId, setDraggedNoteId] = useState<string | null>(null)
+  const [dragOverNotebookId, setDragOverNotebookId] = useState<string | null>(null)
+
+  const startDrag = useCallback((noteId: string) => {
+    setDraggedNoteId(noteId)
+  }, [])
+
+  const endDrag = useCallback(() => {
+    setDraggedNoteId(null)
+    setDragOverNotebookId(null)
+  }, [])
+
+  const dragOver = useCallback((notebookId: string | null) => {
+    setDragOverNotebookId(notebookId)
+  }, [])
+
+  const isDragging = draggedNoteId !== null
+  const isDragOver = dragOverNotebookId !== null
+
+  return (
+    <NotebookDragContext.Provider
+      value={{
+        draggedNoteId,
+        dragOverNotebookId,
+        startDrag,
+        endDrag,
+        dragOver,
+        isDragging,
+        isDragOver,
+      }}
+    >
+      {children}
+    </NotebookDragContext.Provider>
+  )
+}