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/app/actions/detect-language.ts

@@ -0,0 +1,12 @@
+'use server'
+
+import { detectUserLanguage } from '@/lib/i18n/detect-user-language'
+import { SupportedLanguage } from '@/lib/i18n/load-translations'
+
+/**
+ * Server action to detect user's preferred language
+ * Called on app load to set initial language
+ */
+export async function getInitialLanguage(): Promise<SupportedLanguage> {
+  return await detectUserLanguage()
+}