feat: add admin edit endpoint for server moderation (#315)

## Summary

Implements `PUT /v0/servers/{id}` admin edit endpoint to address part of
issue #182, providing an API-based solution for server moderation
without requiring direct database access.

- **New endpoint**: `PUT /v0/servers/{id}` for editing existing servers
- **Security**: Uses existing JWT auth with `PermissionActionEdit`
permissions
- **Anti-undelete protection**: Added `ServerStatusDeleted` status that
cannot be reverted
- **Full implementation**: Database, service, API, and comprehensive
test coverage

## Key Use Cases

- Mark malicious servers as `deleted` for takedown
- Update server metadata for moderation actions

Related to: https://github.com/modelcontextprotocol/registry/issues/182
(but that is not _done_ yet because we need admins to be able to login
(probably with #283), and need to add docs on how to do the takedown,
and probably guidelines on what we will/won't takedown)

internal/database/database.go

@@ -28,6 +28,8 @@ type Database interface {
 	Publish(ctx context.Context, serverDetail model.ServerDetail, publisherExtensions map[string]interface{}, registryMetadata model.RegistryMetadata) (*model.ServerRecord, error)
 	// UpdateLatestFlag updates the is_latest flag for a specific server record
 	UpdateLatestFlag(ctx context.Context, id string, isLatest bool) error
+	// UpdateServer updates an existing server record with new server details
+	UpdateServer(ctx context.Context, id string, serverDetail model.ServerDetail, publisherExtensions map[string]interface{}) (*model.ServerRecord, error)
 	// ImportSeed imports initial data from a seed file
 	ImportSeed(ctx context.Context, seedFilePath string) error
 	// Close closes the database connection