feat(hypridle): define config in home-manager with per-host timeouts

Replace the static hypridle.conf with services.hypridle.settings and add required timeout options so each host tunes its own values:

- idols-ai (PC): 15 min keyboard, 20 min screen-off, 30 min lock.
- 12kingdoms-shoukei (laptop): 3 / 6 / 20 min (previous values).

The options have no defaults because the right values depend on the machine. Update the home-manager eval test to inspect the settings option instead of the old config file text.

home/hosts/linux/idols-ai.nix

@@ -10,6 +10,13 @@ in
   modules.desktop.gaming.enable = true;
   modules.desktop.niri.enable = true;
 
+  # PC: keep the screen on longer than on the laptop.
+  modules.desktop.hypridle = {
+    keyboardBacklightTimeout = 900;
+    screenOffTimeout = 1200;
+    lockTimeout = 1800;
+  };
+
   programs.zed-editor.userSettings = {
     ui_font_size = 18.0;
     buffer_font_size = 17.0;