Add client eviction feature

- Add EvictClient method to DHCP Server
- Add /api/dhcp/leases/evict endpoint to force client IP release
- Add 'Evict' button in Web UI for online clients
- Update table layout to include Action column
- Evicted client will be forced to get a new IP on next DHCP request

internal/web/server.go

@@ -117,6 +117,7 @@ func (s *Server) setupRoutes() {
 		protected.GET("/dhcp/bindings", s.handleGetBindings)
 		protected.POST("/dhcp/bindings", s.handleCreateBinding)
 		protected.DELETE("/dhcp/bindings/:id", s.handleDeleteBinding)
+		protected.POST("/dhcp/leases/evict", s.handleEvictClient)
 		
 		// DNS
 		protected.GET("/dns/config", s.handleGetDNSConfig)
@@ -282,6 +283,30 @@ func (s *Server) handleDeleteBinding(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{"message": "Binding deleted"})
 }
 
+func (s *Server) handleEvictClient(c *gin.Context) {
+	var req struct {
+		MAC string `json:"mac"`
+		IP  string `json:"ip"`
+	}
+	
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+	
+	if req.MAC == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "MAC is required"})
+		return
+	}
+	
+	if err := s.dhcpServer.EvictClient(req.MAC); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+	
+	c.JSON(http.StatusOK, gin.H{"message": "Client evicted successfully"})
+}
+
 func (s *Server) handleGetRecords(c *gin.Context) {
 	records, err := s.dnsServer.GetDNSRecords()
 	if err != nil {