fix: idle detection errors and system freezes after hibernation

- Test idle detection methods only once during initialization to prevent repeated failures
- Add snap environment detection with automatic method filtering
- Add proper snap plugs for system-observe and login-session-observe interfaces
- Improve DBus handling by trying gdbus first (works better in snap environments)
- Add rate-limited error logging to prevent log spam
- Add snap install hook to guide users on connecting required interfaces
- Ensure graceful fallback to 0 (not idle) when detection fails

This prevents the system freezes that occurred after hibernation due to repeated
failing idle detection attempts, and improves snap compatibility for DBus access.

electron-builder.yaml

@@ -61,6 +61,19 @@ snap:
   autoStart: true
   base: core22
   confinement: strict
+  plugs:
+    - default
+    - desktop
+    - desktop-legacy
+    - wayland
+    - x11
+    - unity7
+    - home
+    - network
+    - browser-support
+    - password-manager-service
+    - system-observe
+    - login-session-observe
 
 mac:
   appId: com.super-productivity.app