Switch musicdolphin from a Pi 4 to a Pi 5

The SD card moves over as is, so:
- pi_standard_setup can install the Pi 5 kernel (linux-image-rpi-2712, an arm64
  package on the armhf userland), which a Pi 4 image lacks. Opt-in via
  pi_standard_setup_install_pi5_kernel.
- The Pi is powered through the HiFiBerry board's GPIO header, so it cannot negotiate
  a 5A supply and would cap USB at 600mA. pi_hifiberry_amp sets
  usb_max_current_enable=1 when hifiberry_powers_pi is true (default false).
- The DHT22 poller is off: Adafruit_DHT bit-bangs BCM283x registers, which the Pi 5
  no longer has (GPIO sits behind the RP1 chip).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

host_vars/musicdolphin.yml

@@ -9,7 +9,16 @@ main_user: root
 
 mediapi_has_hifiberry_amp: true
 mediapi_ir_control: irserver
-mediapi_has_dhtsensor: true
+# Off for the Pi 5: the legacy Adafruit_DHT library bit-bangs the BCM283x registers,
+# which the Pi 5 no longer has (GPIO sits behind the RP1 chip), so the poller cannot
+# work there. Needs a libgpiod-based replacement before this goes back to true.
+mediapi_has_dhtsensor: false
+
+# Raspberry Pi 5. The SD card came from a Pi 4, whose image has no Pi 5 kernel.
+pi_standard_setup_install_pi5_kernel: true
+# The Pi is fed 5V through the HiFiBerry board's GPIO header, not USB-C, so it cannot
+# negotiate a 5A supply and would cap USB current at 600mA.
+hifiberry_powers_pi: true
 
 # Display-only MusicMouse instance: no physical mouse attached, shown on the monitor
 # via pi_kiosk instead. See roles/pi_musicmouse/files/config-musicdolphin.yml.