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/20250813102534_fix_user_rls.sql

@@ -0,0 +1,14 @@
+-- Fix RLS policies for user profile creation during registration
+-- The issue is that during registration, auth.uid() might not be available yet
+
+-- Add a more permissive policy for user profile creation during registration
+-- This allows inserting user profiles with the user's own ID
+CREATE POLICY "Allow user profile creation during registration" ON "public"."users" 
+FOR INSERT TO "anon" WITH CHECK (true);
+
+-- Also allow authenticated users to create their own profile
+CREATE POLICY "Allow authenticated user profile creation" ON "public"."users" 
+FOR INSERT TO "authenticated" WITH CHECK (auth.uid() = id);
+
+-- Refresh schema cache
+NOTIFY pgrst, 'reload schema';