Remove namespace match validation for websiteUrl and remote URL (#769)

<!-- Provide a brief summary of your changes -->

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->

Resolve https://github.com/modelcontextprotocol/registry/issues/768 and
https://github.com/modelcontextprotocol/registry/issues/494.

Require HTTPS for remote URLs. Currently all remote URLs on the MCP
Registry are HTTPS.
Also fix a test bug when running on Windows (bad temp path).

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

Unit tests.
Published a server.json locally with a website URL not matching the
server name.

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [ ] ~I have added or updated documentation as needed~ N/A

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

internal/importer/importer_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/modelcontextprotocol/registry/internal/config"
@@ -20,7 +21,7 @@ import (
 
 func TestImportService_LocalFile(t *testing.T) {
 	// Create a temporary seed file
-	tempFile := "/tmp/test_import_seed.json"
+	tempFile := filepath.Join(os.TempDir(), "test_import_seed.json")
 	seedData := []*apiv0.ServerJSON{
 		{
 			Schema:      model.CurrentSchemaURL,