feat: 新增 MCP 模块

- mcp_handler.go, mcp.go, mcp_repo.go, mcp_service.go

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/internal/service/mcp_service.go

@@ -0,0 +1,42 @@
+package service
+
+import (
+	"x-agents/server/internal/model"
+	"x-agents/server/internal/repository"
+)
+
+type MCPService struct {
+	mcpRepo *repository.MCPRepository
+}
+
+func NewMCPService(mcpRepo *repository.MCPRepository) *MCPService {
+	return &MCPService{mcpRepo: mcpRepo}
+}
+
+func (s *MCPService) GetAllMCPs() ([]model.MCP, error) {
+	return s.mcpRepo.FindAll()
+}
+
+func (s *MCPService) GetMCPByID(id string) (*model.MCP, error) {
+	return s.mcpRepo.FindByID(id)
+}
+
+func (s *MCPService) GetMCPByName(name string) (*model.MCP, error) {
+	return s.mcpRepo.FindByName(name)
+}
+
+func (s *MCPService) GetMCPsByCategory(category string) ([]model.MCP, error) {
+	return s.mcpRepo.FindByCategory(category)
+}
+
+func (s *MCPService) CreateMCP(mcp *model.MCP) error {
+	return s.mcpRepo.Create(mcp)
+}
+
+func (s *MCPService) UpdateMCP(mcp *model.MCP) error {
+	return s.mcpRepo.Update(mcp)
+}
+
+func (s *MCPService) DeleteMCP(id string) error {
+	return s.mcpRepo.Delete(id)
+}