fix: sync Genshin HDR toggle with the actual game registry state

[loliri]

Summary

• The Genshin HDR switch in game settings was initialized from AppConfig.EnableGenshinHDR only, so it could disagree with the game's real setting after HDR was toggled in-game or written by another tool
• Add GameSettingService.GetGenshinEnableHDR reading the WINDOWS_HDR_ON_h3132281285 registry value (hk4e only), the read-side counterpart of the existing SetGenshinEnableHDR
• The page now prefers the registry state and falls back to AppConfig when unavailable (non-hk4e, registry read failure, or value not present)

Test plan

• Launch Genshin with HDR enabled in-game → the switch in Starward shows ON on page load
• Toggle HDR off in-game, reopen the game settings page → the switch shows OFF
• Non-Genshin games → switch still initializes from AppConfig as before