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_README.md

@@ -68,6 +68,37 @@ docker run -d \
 
 *Either `AUTH_TOKEN` or `AUTH_TOKEN_FILE` must be set for HTTP mode. If both are set, `AUTH_TOKEN` takes precedence.
 
+### Configuration File Support (v2.8.2+)
+
+You can mount a JSON configuration file to set environment variables:
+
+```bash
+# Create config file
+cat > config.json << EOF
+{
+  "MCP_MODE": "http",
+  "AUTH_TOKEN": "your-secure-token",
+  "LOG_LEVEL": "info",
+  "N8N_API_URL": "https://your-n8n-instance.com",
+  "N8N_API_KEY": "your-api-key"
+}
+EOF
+
+# Run with config file
+docker run -d \
+  --name n8n-mcp \
+  -v $(pwd)/config.json:/app/config.json:ro \
+  -p 3000:3000 \
+  ghcr.io/czlonkowski/n8n-mcp:latest
+```
+
+The config file supports:
+- All standard environment variables
+- Nested objects (flattened with underscore separators)
+- Arrays, booleans, numbers, and strings
+- Secure handling with command injection prevention
+- Dangerous variable blocking for security
+
 ### Docker Compose Configuration
 
 The default `docker-compose.yml` provides:
@@ -142,6 +173,19 @@ docker run --rm -i --init \
   ghcr.io/czlonkowski/n8n-mcp:latest
 ```
 
+### Server Mode (Command Line)
+
+You can also use the `serve` command to start in HTTP mode:
+
+```bash
+# Using the serve command (v2.8.2+)
+docker run -d \
+  --name n8n-mcp \
+  -e AUTH_TOKEN=your-secure-token \
+  -p 3000:3000 \
+  ghcr.io/czlonkowski/n8n-mcp:latest serve
+```
+
 Configure Claude Desktop:
 ```json
 {