Update MEmu and BlueStacks emulators to Android 13

- Change MEmu ANDROID_VERSION from "126" (Android 12) to "136" (Android 13)
- Change BlueStacks instance name from "pyclashbot-96" to "pyclashbot-136"
- Replace hardcoded "pyclashbot-126" strings with EMULATOR_NAME constant
- Improve user-facing messages to specify Android 13 when no instance is found