Fix pgAdmin email validation and add SQL verification queries

PGADMIN FIX:

- Changed email from admin@businessanalytics.local to admin@example.com

- pgAdmin rejects .local domains as invalid email addresses

- Updated all documentation with correct email

SETUP VERIFICATION:

- Added 5 SQL verification queries to setup-database.sh

- Query 1: Sample countries (top 5)

- Query 2: Sample merchant categories (top 5)

- Query 3: All transaction types with descriptions

- Query 4: All fraud types ordered by severity

- Query 5: All customer segments with descriptions

BENEFITS:

- Users can immediately see that data was loaded correctly

- Provides visual confirmation of schema setup

- Shows sample data structure before generating full dataset

- Helps troubleshoot setup issues early

README.md

@@ -163,7 +163,7 @@ http://localhost:3000
 ```
 
 **Login credentials:**
-- Email: `admin@businessanalytics.local`
+- Email: `admin@example.com`
 - Password: `SecurePass123!`
 
 **First time setup:**