refactor: consolidate blockchain explorer into single app and update backup ignore patterns

- Remove standalone explorer-web app (README, HTML, package files)
- Add /web endpoint to blockchain-explorer for web interface access
- Update .gitignore to exclude application backup archives (*.tar.gz, *.zip)
- Add backup documentation files to .gitignore (BACKUP_INDEX.md, README.md)
- Consolidate explorer functionality into main blockchain-explorer application

apps/exchange/scripts/setup_postgresql.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+echo "=== PostgreSQL Setup for AITBC Exchange ==="
+echo ""
+
+# Install PostgreSQL if not already installed
+if ! command -v psql &> /dev/null; then
+    echo "Installing PostgreSQL..."
+    sudo apt-get update
+    sudo apt-get install -y postgresql postgresql-contrib
+fi
+
+# Start PostgreSQL service
+sudo systemctl start postgresql
+sudo systemctl enable postgresql
+
+# Create database and user
+echo "Creating database and user..."
+sudo -u postgres psql -c "CREATE DATABASE aitbc_exchange;"
+sudo -u postgres psql -c "CREATE USER aitbc_user WITH PASSWORD 'aitbc_password';"
+sudo -u postgres psql -c "GRANT ALL PRIVILEGES ON DATABASE aitbc_exchange TO aitbc_user;"
+
+# Test connection
+echo "Testing connection..."
+sudo -u postgres psql -c "\l" | grep aitbc_exchange
+
+echo ""
+echo "✅ PostgreSQL setup complete!"
+echo ""
+echo "Connection details:"
+echo "  Host: localhost"
+echo "  Port: 5432"
+echo "  Database: aitbc_exchange"
+echo "  User: aitbc_user"
+echo "  Password: aitbc_password"
+echo ""
+echo "You can now run the migration script."