test(media): add selected TURN allocation gate (#122)

Add a sanitized standalone Chrome allocation gate and retain the active Host-ingress selected TURN functional evidence. Ordinary peers remain STUN-only; initial ingress, peer-selected, mobile, resource, and performance gates remain open.

src/server/config.ts

@@ -202,7 +202,7 @@ function parseStunUrlList(value: string | undefined): string[] {
   });
 }
 
-function parseSelectedEdgeTurn(
+export function parseSelectedEdgeTurn(
   environment: NodeJS.ProcessEnv,
 ): SelectedEdgeTurnConfig | undefined {
   const names = [