Add safe .env.example with placeholders

.env.example

@@ -0,0 +1,23 @@
+# Neo4j Configuration
+NEO4J_AUTH=neo4j/your_password
+NEO4J_BOLT_URL=bolt://neo4j:7687
+
+# PostgreSQL Configuration
+POSTGRES_PASSWORD=your_postgres_password
+POSTGRES_CONNECTION=postgresql://postgres:your_password@postgres:5432/your_db
+
+# MCP Server Configuration
+MCP_API_KEYS=your-api-key
+MCP_PORT=8000
+
+# Agent Configuration
+AGENT_POLL_INTERVAL=30
+PAUSE_DURATION=300
+
+# LLM Configuration
+LLM_API_KEY=your-llm-api-key
+LLM_MODEL=gpt-4o
+
+# Development Settings
+COMPOSE_PROJECT_NAME=agent-mcp-sql
+DOCKER_BUILDKIT=1