feat(socket-handler): implement direct socket passing for DNS and email services

- Add socket-handler mode eliminating internal port binding for improved performance
- Add `dnsDomain` config option for automatic DNS-over-HTTPS (DoH) setup
- Add `useSocketHandler` flag to email config for direct socket processing
- Update SmartProxy route generation to support socket-handler actions
- Integrate smartdns with manual HTTPS mode for DoH without port binding
- Add automatic route creation for DNS paths when dnsDomain is configured
- Update documentation with socket-handler configuration and benefits
- Improve resource efficiency by eliminating internal port forwarding

readme.md

@@ -212,6 +212,7 @@ interface IDcRouterOptions {
     tls?: ITlsConfig;
     maxMessageSize?: number;
     rateLimits?: IRateLimitConfig;
+    useSocketHandler?: boolean;     // Enable socket-handler mode (no port binding)
   };
   
   // DNS server configuration
@@ -221,6 +222,9 @@ interface IDcRouterOptions {
     records?: IDnsRecord[];
   };
   
+  // DNS domain for automatic DNS-over-HTTPS setup
+  dnsDomain?: string;               // e.g., 'dns.example.com'
+  
   // TLS and certificate configuration
   tls?: {
     contactEmail: string;
@@ -262,6 +266,71 @@ interface IRouteConfig {
 }
 ```
 
+## Socket-Handler Mode
+
+DcRouter supports an advanced socket-handler mode that eliminates internal port binding for both DNS and email services. Instead of services listening on internal ports, SmartProxy passes sockets directly to the services.
+
+### DNS Socket-Handler
+
+When `dnsDomain` is configured, DcRouter automatically:
+- Sets up DNS server for UDP on port 53
+- Creates SmartProxy routes for DNS-over-HTTPS (DoH) on the specified domain
+- Uses socket-handler for HTTPS/DoH traffic (no HTTPS port binding)
+
+```typescript
+const router = new DcRouter({
+  dnsDomain: 'dns.example.com',    // Enables DNS with DoH
+  smartProxyConfig: {
+    // DNS routes are automatically created
+  }
+});
+```
+
+This creates:
+- UDP DNS service on port 53 (standard DNS queries)
+- HTTPS routes for `dns.example.com/dns-query` and `dns.example.com/resolve`
+- Automatic TLS certificates via Let's Encrypt
+
+### Email Socket-Handler
+
+When `useSocketHandler` is enabled in email config:
+- Email server doesn't bind to any ports
+- SmartProxy passes sockets directly to email handlers
+- Reduces latency and resource usage
+
+```typescript
+const router = new DcRouter({
+  emailConfig: {
+    ports: [25, 587, 465],
+    hostname: 'mail.example.com',
+    useSocketHandler: true,         // Enable socket-handler mode
+    routes: [/* email routes */]
+  }
+});
+```
+
+### Benefits of Socket-Handler Mode
+
+1. **Performance**: Eliminates internal port forwarding overhead
+2. **Security**: No exposed internal ports
+3. **Resource Efficiency**: Fewer open ports and listeners
+4. **Simplified Networking**: Direct socket passing
+5. **Automatic Configuration**: Routes created automatically
+
+### Traditional vs Socket-Handler Mode
+
+**Traditional Mode (default):**
+```
+External Port → SmartProxy → Internal Port → Service
+    25             →           10025          → Email
+```
+
+**Socket-Handler Mode:**
+```
+External Port → SmartProxy → Socket Handler → Service
+    25             →         (direct socket)  → Email
+```
+
 ## Email System
 
 ### Email Route Actions