Add filtering functionality to server list endpoint (#374)

## Summary
- Adds `updated_since`, `search`, and `version` query parameters to `GET
/v0/servers`
- Enables incremental synchronization via RFC3339 timestamp filtering
- Provides simple substring search on server names
- Supports latest version filtering with `version=latest`

This implementation provides the core filtering capabilities needed for
efficient registry synchronization and improved server discovery.

Fixes #291
Fixes #135

internal/service/registry_service.go

@@ -29,8 +29,8 @@ func NewRegistryService(db database.Database, cfg *config.Config) RegistryServic
 	}
 }
 
-// List returns registry entries with cursor-based pagination in flattened format
-func (s *registryServiceImpl) List(cursor string, limit int) ([]apiv0.ServerJSON, string, error) {
+// List returns registry entries with cursor-based pagination and optional filtering
+func (s *registryServiceImpl) List(filter *database.ServerFilter, cursor string, limit int) ([]apiv0.ServerJSON, string, error) {
 	// Create a timeout context for the database operation
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
@@ -40,8 +40,8 @@ func (s *registryServiceImpl) List(cursor string, limit int) ([]apiv0.ServerJSON
 		limit = 30
 	}
 
-	// Use the database's ListServers method with pagination
-	serverRecords, nextCursor, err := s.db.List(ctx, nil, cursor, limit)
+	// Use the database's ListServers method with pagination and filtering
+	serverRecords, nextCursor, err := s.db.List(ctx, filter, cursor, limit)
 	if err != nil {
 		return nil, "", err
 	}

internal/service/service.go

@@ -1,13 +1,14 @@
 package service
 
 import (
+	"github.com/modelcontextprotocol/registry/internal/database"
 	apiv0 "github.com/modelcontextprotocol/registry/pkg/api/v0"
 )
 
 // RegistryService defines the interface for registry operations
 type RegistryService interface {
-	// Retrieve all servers
-	List(cursor string, limit int) ([]apiv0.ServerJSON, string, error)
+	// Retrieve all servers with optional filtering
+	List(filter *database.ServerFilter, cursor string, limit int) ([]apiv0.ServerJSON, string, error)
 	// Retrieve a single server by registry metadata ID
 	GetByID(id string) (*apiv0.ServerJSON, error)
 	// Publish a server