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/components/admin-content-area.tsx

@@ -0,0 +1,19 @@
+import { cn } from '@/lib/utils'
+
+export interface AdminContentAreaProps {
+  children: React.ReactNode
+  className?: string
+}
+
+export function AdminContentArea({ children, className }: AdminContentAreaProps) {
+  return (
+    <main
+      className={cn(
+        'flex-1 bg-gray-50 dark:bg-zinc-950 p-6',
+        className
+      )}
+    >
+      {children}
+    </main>
+  )
+}