Deploy rearchitected MusicMouse backend + web frontend

The app grew a python-backend/ and a web/ frontend, so pi_musicmouse no
longer matches it. Rework the role:

- Install a pinned uv and build the venv with Python 3.13; Raspbian
  Bookworm's python3 is 3.11 and the backend uses PEP 695 syntax.
- pip install python-backend/ instead of a requirements.txt, and take
  the systemd unit straight from the checkout so it can't drift.
- Build web/ on the control machine (no npm on the Pi) and rsync
  web/dist over. Chain the checkout -> install -> build -> sync -> restart
  steps through handlers so a run with no repo change does nothing.
- Per-host config files (config-<host>.yml); the schema now differs
  between a host with a real mouse and a display-only one.
- Version to deploy is per host (musicmouse_version), no default.

Add pi_kiosk: autologin user running startx with Firefox in kiosk mode
and no window manager, for a Pi with a monitor attached. Enabled by
mediapi_has_monitor, defaulting off.

Turn musicdolphin into a display-only instance: serial and audio
simulated, driven entirely through the kiosk page.

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

roles/pi_musicmouse/files/config-musicdolphin.yml

@@ -0,0 +1,29 @@
+---
+# musicdolphin: display-only instance. No physical mouse attached (for
+# now), so serial and audio are both "simulate" - the web front-end (shown locally in
+# the pi_kiosk role's Firefox kiosk window, and reachable on the LAN for a tablet) is a
+# complete way to drive the player on its own. `figures` still needs at least one entry
+# (the schema requires it) even though nothing will ever scan a tag here.
+general:
+  library:
+    root: /media/musicmouse
+
+  serial_port: "simulate"
+  alsa_device: "simulate"
+
+  web:
+    host: "0.0.0.0"
+    port: 8080
+    static_dir: /opt/musicmouse/web/dist
+
+  button_leds_brightness: 0.5
+  volume_increment: 5
+  min_volume: 0
+  max_volume: 100
+
+figures:
+  # Placeholder - serial_port is "simulate" so no reader ever reports a tag id, but the
+  # schema requires at least one figure to be configured.
+  placeholder:
+    id: "0000000001"
+    colors: ["#ffffff", "#ffffff", "#000000", "#ffffff"]

roles/pi_musicmouse/files/config-musicmouse.yml

@@ -1,17 +1,26 @@
 ---
 general:
+  library:
+    root: /media/musicmouse
+
+  serial_port: "/dev/ttyUSB0"
   alsa_device: softvol_effects
   mqtt:
     user: musicmouse
     password: KNLEFLZF94yA6Zhj141
     server: homeassistant
-  hass_url: https://ha.bauer.tech
-  hass_token: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiI4N2ExMzM2ZmQ4ZWQ0ZDgzOWZhMjU3NmZjYTg1NWQ1ZiIsImlhdCI6MTcwNDAyOTUyOSwiZXhwIjoyMDE5Mzg5NTI5fQ.vx9L5bTSey98uc8TwodShaEXSMr-hjXugPsNviR_fEw" # noqa: yaml[line-length]
+  web:
+    host: "0.0.0.0"
+    port: 8080
+    static_dir: /opt/musicmouse/web/dist
+
+  # The old hass_url/hass_token keys don't exist in the current schema - HA
+  # integration now lives under general.ha (url, token, devices, scenes; needs at
+  # least one device or scene) - see config.yml.example. Add it back once picked.
   button_leds_brightness: 0.5
   volume_increment: 5
   min_volume: 23
   max_volume: 70
-  serial_port: "/dev/ttyUSB0"
 
 figures:
   elefant:

roles/pi_musicmouse/files/musicmouse.service

@@ -1,11 +0,0 @@
-[Unit]
-Description=MusicMouse Player
-After=network.target
-
-[Service]
-Type=simple
-Restart=always
-ExecStart=/opt/musicmouse_venv/bin/python /opt/musicmouse/espmusicmouse/host_driver/main.py /media/musicmouse/
-
-[Install]
-WantedBy=multi-user.target