fix: add Docker configuration file support (fixes #105)

This commit adds comprehensive support for JSON configuration files in Docker containers,
addressing the issue where the Docker image fails to start in server mode and ignores
configuration files.

## Changes

### Docker Configuration Support
- Added parse-config.js to safely parse JSON configs and export as shell variables
- Implemented secure shell quoting to prevent command injection
- Added dangerous environment variable blocking for security
- Support for all JSON data types with proper edge case handling

### Docker Server Mode Fix
- Added support for "n8n-mcp serve" command in entrypoint
- Properly transforms serve command to HTTP mode
- Fixed missing n8n-mcp binary issue in Docker image

### Security Enhancements
- POSIX-compliant shell quoting without eval
- Blocked dangerous variables (PATH, LD_PRELOAD, etc.)
- Sanitized configuration keys to prevent invalid shell variables
- Protection against shell metacharacters in values

### Testing
- Added 53 comprehensive tests for Docker configuration
- Unit tests for parsing, security, and edge cases
- Integration tests for Docker entrypoint behavior
- Security-focused tests for injection prevention

### Documentation
- Updated Docker README with config file mounting examples
- Enhanced troubleshooting guide with config file issues
- Added version bump to 2.8.2

### Additional Files
- Included deployment-engineer and technical-researcher agent files

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/DOCKER_TROUBLESHOOTING.md

@@ -14,6 +14,41 @@ This guide helps resolve common issues when running n8n-mcp with Docker, especia
 
 ## Common Issues
 
+### Docker Configuration File Not Working (v2.8.2+)
+
+**Symptoms:**
+- Config file mounted but environment variables not set
+- Container starts but ignores configuration
+- Getting "permission denied" errors
+
+**Solutions:**
+
+1. **Ensure file is mounted correctly:**
+```bash
+# Correct - mount as read-only
+docker run -v $(pwd)/config.json:/app/config.json:ro ...
+
+# Check if file is accessible
+docker exec n8n-mcp cat /app/config.json
+```
+
+2. **Verify JSON syntax:**
+```bash
+# Validate JSON file
+cat config.json | jq .
+```
+
+3. **Check Docker logs for parsing errors:**
+```bash
+docker logs n8n-mcp | grep -i config
+```
+
+4. **Common issues:**
+- Invalid JSON syntax (use a JSON validator)
+- File permissions (should be readable)
+- Wrong mount path (must be `/app/config.json`)
+- Dangerous variables blocked (PATH, LD_PRELOAD, etc.)
+
 ### Custom Database Path Not Working (v2.7.16+)
 
 **Symptoms:**