Figures: several albums per figure, picked on the LED ring

A figure folder that holds album folders instead of audio can play any of them,
up to six, in folder order (depth-first, alphabetical). Each is its own album,
titled "Fuchs - <folder>" and of the figure's kind. Putting the figure down plays
the album it played last, or the first, straight away; another figure placed in
between forgets the position in that album, not the album itself.

Meanwhile the ring offers all of them: one section per album from a fixed palette,
edges shifting towards the neighbours' hue, the selected one bright and wobbling.
The knob moves the selection one section per detent and wraps; pressing plays the
selected album, and left alone for 8 s the picker fades into the figure's colours
and the music carries on. While open, the device hands the knob to the picker
(`capture_knob`): turns do not change the volume and the press is not published to
Home Assistant. A tick per step and a confirm "pling" go with it.

The firmware only draws: one new ring effect, LED_WHEEL_EFFECT_SEGMENT_SELECT (23),
re-sent on every detent with the section to glide from. The look is tunable through
a temporary `general.figure_selection` config section until the right values
become constants.

Every UI sound - the screen's blubb, the parents' timer, the picker - now follows
the music volume with a floor, times a new parent-mode "Effekt-Lautstärke"
(`general.effects_volume`).

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

web/src/api/types.ts

@@ -111,6 +111,8 @@ export interface Settings {
   initial_volume: number;
   volume_increment: number;
   button_leds_brightness: number;
+  /** UI sounds (screen, timer, album picker) relative to the music, in percent. */
+  effects_volume: number;
   /** Minutes without music before the device's screen switches itself off, 0 = never.
    * `null` when there is no screen to switch (no `off_command` configured). */
   screen_auto_off_minutes: number | null;

web/src/components/ParentPanel.tsx

@@ -55,6 +55,7 @@ const FIELDS: Array<[AlwaysSetting, string, string, number, number, number]> = [
   ["initial_volume", "Start-Lautstärke", "Beim Einschalten", 0, 200, 1],
   ["volume_increment", "Schritt am Drehknopf", "Pro Rasterung", 1, 100, 1],
   ["button_leds_brightness", "Tastenbeleuchtung", "0 bis 1", 0, 1, 0.05],
+  ["effects_volume", "Effekt-Lautstärke", "Klicks und Signaltöne, in % der Musik", 0, 100, 5],
 ];
 
 function NumberField({