Close the gaps the cross-UI audit found

Audited bar, dock, quick settings, date menu and Settings for three
things: a setting reachable in one UI but not another, a setting that
exists but is unreachable anywhere, and UI that states something false.

Night Light was fully exposed in Quick Settings and had no control
anywhere in Settings. It now has a card on Displays, where GNOME also
puts it, with on/off, schedule, times and temperature.

Adding those controls would have shipped the exact defect this audit
exists to find. NightLight declared enabled, temperature and automatic
as bindings on the store, but toggle() assigns to them, and an
assignment destroys a QML binding permanently -- so the service wrote to
the store and never read from it again. The Settings controls would have
written values the service ignored, while Quick Settings kept working.
It now follows the store. Every other service was swept for the same
pattern; this was the only one.

The night light schedule was two hardcoded literals, so the hours could
not be changed. They are schema keys now, with a row that renders 17.5
as "5:30 PM" and honours the 24-hour preference rather than showing a
decimal nobody reads as a time.

keyboardLayout was in the schema and read by input.lua but had no
control anywhere: configurable in principle, unreachable in practice. It
is surfaced on Input & Shortcuts as read-only, with the reason, because
it needs a compositor reload and a control implying instant apply would
be a smaller lie but still a lie.

Caffeine was a Quick Settings toggle mentioned only in a subtitle in
Settings. It has a real control now.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

config/dot/quickshell/services/NightLight.qml

@@ -89,6 +89,34 @@ Singleton {
     onEnabledChanged: DesktopPreferences.set("nightLightEnabled", root.enabled)
     onAutomaticChanged: DesktopPreferences.set("nightLightAutomatic", root.automatic)
 
+    // `enabled`, `temperature`, and `automatic` are declared as bindings on the
+    // store, but a binding is destroyed the moment anything assigns to the
+    // property -- which toggle() does. Without this, the service would write to
+    // the store and never read from it again: Quick Settings would keep working
+    // while the same settings on the Displays page silently did nothing, which
+    // is worse than not offering them there at all.
+    //
+    // No loop: set() is a no-op when the value is unchanged, and assigning a
+    // property its current value emits nothing, so this converges immediately.
+    Connections {
+        target: DesktopPreferences
+        function onRevisionChanged(): void { root.syncFromStore(); }
+    }
+
+    function syncFromStore(): void {
+        const storedEnabled = DesktopPreferences.get("nightLightEnabled") === true;
+        if (root.enabled !== storedEnabled)
+            root.enabled = storedEnabled;
+
+        const storedAutomatic = DesktopPreferences.get("nightLightAutomatic") === true;
+        if (root.automatic !== storedAutomatic)
+            root.automatic = storedAutomatic;
+
+        const storedTemperature = DesktopPreferences.get("nightLightTemperature");
+        if (typeof storedTemperature === "number" && root.temperature !== storedTemperature)
+            root.temperature = storedTemperature;
+    }
+
     onActiveChanged: {
         if (!root.initialized)
             return;