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/20250813102533_fix_organization_rls.sql

@@ -0,0 +1,13 @@
+-- Fix RLS policies for organization creation during registration
+-- Allow anonymous users to create organizations during signup
+
+-- Add policy for anonymous organization creation
+CREATE POLICY "Allow organization insert for anon during registration" ON "public"."organizations" 
+FOR INSERT TO "anon" WITH CHECK (true);
+
+-- Add policy for anonymous organization selection (needed to get the created org)
+CREATE POLICY "Allow organization select for anon during registration" ON "public"."organizations" 
+FOR SELECT TO "anon" USING (true);
+
+-- Refresh schema cache
+NOTIFY pgrst, 'reload schema';