IR remote: power key switches the screen; count irserver's repeats

KEY_POWER emits ToggleScreenRequested, which a new ScreenService turns into the
optional general.screen.toggle_command (musicdolphin: ansible's kiosk-screen). It is
a service, not a reaction, so the subprocess runs in its own task instead of holding
the bus; a press while one is still running is dropped, and failures, hangs and a
missing command are only logged.

irserver reports every line of a held button as repeat 00, so a slightly long press
on Next skipped several tracks and Power would switch the screen off and on again.
A line of the same button within 0.25s of the previous one now counts as a repeat.

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

python-backend/config.yml.example

@@ -94,9 +94,17 @@ general:
     port: 2222                 # this deployment's lircd listens on 2222, not its own
                                 # default of 8765 - see the ansible role
     remote_name: "Hauppauge"   # other remotes registered with the same lircd (an LED
-                                # remote, say) are ignored
+                                # remote, say) are ignored (case-insensitively)
     reconnect_interval: 5.0
 
+  # The attached monitor, switched by the remote's power key. Omit the section on a
+  # device without one and the key does nothing. The command runs on every press, split
+  # shell-style but not through a shell; it decides itself whether that means on or off
+  # (ansible's pi_kiosk installs kiosk-screen for this).
+  # screen:
+  #   toggle_command: "/usr/local/bin/kiosk-screen toggle"
+  #   timeout: 5.0               # seconds before a hung command is killed
+
   # Home Assistant integration. Omit the whole section to run without MQTT.
   # The backend exposes three lights, a player sensor, a volume slider, transport
   # buttons, device triggers for every button/touch area, and a tag scanner.