Add power settings for the lighting, bump to 1.4.0

New Power page:
- toggle for the firmware's 30 s keyboard backlight timeout
- idle timeout for keyboard and lightbar, separately for AC and battery;
  predatord watches all input devices and restores the lighting on the
  next input
- battery rules: dimmed keyboard brightness, keyboard off, lightbar off

The rules only change what is sent to the hardware; the saved lighting
settings stay untouched.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

predator_control/idle.py

@@ -0,0 +1,56 @@
+"""Input activity watcher used for the 'turn lighting off when idle' feature."""
+
+import glob
+import os
+import select
+import threading
+import time
+
+
+class IdleWatcher(threading.Thread):
+    """Tracks the time of the last keyboard/touchpad/mouse event on any input device."""
+
+    RESCAN = 30  # seconds between scans for new devices (hotplug, resume)
+
+    def __init__(self, on_activity=None):
+        super().__init__(daemon=True)
+        self.last_input = time.monotonic()
+        self.on_activity = on_activity
+
+    def idle_seconds(self):
+        return time.monotonic() - self.last_input
+
+    def _open_all(self, fds):
+        for path in glob.glob("/dev/input/event*"):
+            if path in fds.values():
+                continue
+            try:
+                fds[os.open(path, os.O_RDONLY | os.O_NONBLOCK)] = path
+            except OSError:
+                pass
+
+    def run(self):
+        fds = {}
+        next_scan = 0.0
+        while True:
+            if time.monotonic() >= next_scan:
+                self._open_all(fds)
+                next_scan = time.monotonic() + self.RESCAN
+            if not fds:
+                time.sleep(5)
+                continue
+            ready, _, _ = select.select(list(fds), [], [], 5)
+            active = False
+            for fd in ready:
+                try:
+                    if os.read(fd, 4096):
+                        active = True
+                except BlockingIOError:
+                    pass
+                except OSError:
+                    os.close(fd)
+                    fds.pop(fd, None)
+            if active:
+                self.last_input = time.monotonic()
+                if self.on_activity:
+                    self.on_activity()