Screensavers (#462)

Adds screensavers in addition to the backlight idle off. 
More info in screensavers.md

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

* **New Features**
  * Added a screensaver system with multiple styles (Bouncing Balls, Mystify, Matrix Rain) and a common screensaver interface; auto-starts after inactivity, dismisses on interaction, and supports auto-off/backlight behavior.
  * New Display setting and UI dropdown to choose and persist the screensaver.

* **Documentation**
  * Added comprehensive screensaver docs covering usage, extension, and configuration.

* **Chores**
  * Registered the display-idle service.

* **Bug Fixes**
  * Updated LVGL API calls to match renamed functions.

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<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Tactility/Source/Tactility.cpp

@@ -53,7 +53,9 @@ namespace service {
     namespace loader { extern const ServiceManifest manifest; }
     namespace memorychecker { extern const ServiceManifest manifest; }
     namespace statusbar { extern const ServiceManifest manifest; }
+#ifdef ESP_PLATFORM
     namespace displayidle { extern const ServiceManifest manifest; }
+#endif
 #if defined(ESP_PLATFORM) && defined(CONFIG_TT_DEVICE_LILYGO_TDECK)
     namespace keyboardidle { extern const ServiceManifest manifest; }
 #endif
@@ -251,7 +253,9 @@ static void registerAndStartSecondaryServices() {
     addService(service::loader::manifest);
     addService(service::gui::manifest);
     addService(service::statusbar::manifest);
+#ifdef ESP_PLATFORM
     addService(service::displayidle::manifest);
+#endif
 #if defined(ESP_PLATFORM) && defined(CONFIG_TT_DEVICE_LILYGO_TDECK)
     addService(service::keyboardidle::manifest);
 #endif