feat: extensible participant status determination for booking creation

Adds a rule-based system to determine participant status in CREATE
payloads. Participants selecting a 'Begleitperson' service now receive
status 'O' (Option), all others default to 'F' (Final).

- Add ParticipantStatusRuleInterface for defining status rules
- Add ParticipantStatusRuleRegistry for priority-based rule evaluation
- Add ChaperonServiceStatusRule for Begleitperson detection
- Integrate status evaluation into BookingPayloadBuilder

src/Form/Service/ParticipantFieldOptionsProvider.php

@@ -285,9 +285,9 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
                     }
                     $priceLabel = (null === $service->price || 0.0 === $service->price)
                         ? 'inkl.'
-                        : number_format($service->price, 2, ',', '.') . ' €';
+                        : number_format($service->price, 2, ',', '.').' €';
 
-                    return $service->label . ' (' . $priceLabel . ')';
+                    return $service->label.' ('.$priceLabel.')';
                 },
                 'choice_attr' => function (?Service $service) use ($bookingDto, $participantIndex) {
                     if (null === $service) {