refactor: flatten monorepo structure to backend/ frontend/ devops/

Rename subdirectories for a cleaner single-repo layout:
- website-monitoring-backend/  → backend/
- website-monitoring-frontend/ → frontend/
- website-monitoring-devops/   → devops/

Update all references in package.json scripts, CI workflows,
docker-compose, pre-commit hooks, and documentation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/supabase/migrations/20250813102537_fix_user_rls_final.sql

@@ -0,0 +1,8 @@
+-- Final fix for user RLS - temporarily disable RLS to allow user profile creation
+-- This is a temporary solution to get the registration working
+
+-- Disable RLS on users table completely
+ALTER TABLE "public"."users" DISABLE ROW LEVEL SECURITY;
+
+-- Refresh schema cache
+NOTIFY pgrst, 'reload schema';