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>

roles/pi_hifiberry_amp/tasks/main.yml

@@ -11,3 +11,13 @@
     regexp: "^#?dtoverlay=hifiberry-amp"
     line: "dtoverlay={{ hifiberry_overlay }}"
   notify: Reboot
+- name: Lift the Pi 5's USB current cap when the HiFiBerry board powers it
+  # A Pi 5 fed over the GPIO header has no USB-C power negotiation, so it assumes a
+  # weak supply and limits USB ports to 600mA. Unknown to a Pi 4, which ignores it.
+  ansible.builtin.lineinfile:
+    path: /boot/firmware/config.txt
+    regexp: "^#?usb_max_current_enable="
+    line: "usb_max_current_enable=1"
+    insertafter: EOF
+  when: hifiberry_powers_pi
+  notify: Reboot