feat: add .env.example template

.env.example

@@ -0,0 +1,15 @@
+# grist-mcp environment configuration
+
+# Server port (default: 3000)
+PORT=3000
+
+# Agent authentication token (required)
+# Generate with: python -c "import secrets; print(secrets.token_urlsafe(32))"
+GRIST_MCP_TOKEN=your-agent-token-here
+
+# Grist API keys (referenced in config.yaml)
+GRIST_WORK_API_KEY=your-work-api-key
+GRIST_PERSONAL_API_KEY=your-personal-api-key
+
+# Optional: Override config path (default: /app/config.yaml)
+# CONFIG_PATH=/app/config.yaml