Replace db-ui with pgAdmin 4 for better cross-platform compatibility

DOCKER COMPOSE:

- Replaced ghcr.io/n7olkachev/db-ui with dpage/pgadmin4:latest

- Added pgadmin_data volume for persistent configuration

- Configured pgAdmin with default credentials

- Port mapping: 3000:80 (pgAdmin runs on port 80 internally)

DOCUMENTATION:

- Updated README.md with pgAdmin login instructions and first-time setup

- Updated QUICKSTART.md with detailed pgAdmin configuration steps

- Added server connection details for easy setup

BENEFITS:

- pgAdmin has proper multi-platform support (linux/amd64, linux/arm64, etc.)

- Industry-standard PostgreSQL management tool

- More features: query builder, schema visualization, data import/export

- Better documentation and community support

README.md

@@ -139,7 +139,7 @@ docker-compose up -d
 
 This starts:
 - **PostgreSQL 16** on port `5432`
-- **DB-UI** web interface on port `3000`
+- **pgAdmin 4** web interface on port `3000`
 
 ### 5. Initialize the Schema
 ```bash
@@ -157,11 +157,26 @@ This starts:
 
 ### 6. Access the Database
 
-**Option A: DB-UI Web Interface**
+**Option A: pgAdmin Web Interface**
 ```
 http://localhost:3000
 ```
 
+**Login credentials:**
+- Email: `admin@businessanalytics.local`
+- Password: `SecurePass123!`
+
+**First time setup:**
+1. After logging in, click "Add New Server"
+2. **General tab:** Name: `Business Analytics`
+3. **Connection tab:**
+   - Host: `postgres`
+   - Port: `5432`
+   - Database: `business_analytics`
+   - Username: `data_analyst`
+   - Password: `SecurePass123!`
+4. Click "Save"
+
 **Option B: Command Line**
 ```bash
 docker exec -it business_analytics_db psql -U data_analyst -d business_analytics
@@ -446,7 +461,7 @@ This project is licensed under the MIT License - see the [LICENSE](LICENSE) file
 ## 🙏 Acknowledgments
 
 - PostgreSQL community
-- DB-UI project (https://github.com/n7olkachev/db-ui)
+- pgAdmin project (https://www.pgadmin.org/)
 - Financial crime investigation best practices
 
 ## 📧 Support