feat: remove room selection field entirely for single room type

addresses #869axcukn

docs/PROJECT_OVERVIEW.md

@@ -85,7 +85,8 @@ The room assignment system allows participants to freely select any room from St
 
 **Key Features:**
 - **Flexible Selection**: All rooms from Step 1 always appear in participant dropdown, regardless of current capacity
-- **Auto-Assignment**: When exactly ONE room type selected, all participants auto-assigned and dropdown disabled
+- **Auto-Assignment**: When exactly ONE room type selected, all participants auto-assigned via `RoomAssignmentService`
+- **Field Display**: Single room type hides dropdown field entirely, displays room label as read-only text
 - **Conflict Resolution**: When participant selects room at capacity, system automatically unassigns minimum participants needed
 - **Unassignment Priority**: Highest index participants unassigned first (keeps applicant and early participants stable)
 - **User Notifications**: Unassigned participants receive warning notifications via toast system
@@ -96,8 +97,11 @@ The room assignment system allows participants to freely select any room from St
   - `detectRoomCapacityConflict()`: Calculates if assignment would exceed capacity
   - `resolveRoomCapacityConflict()`: Unassigns minimum participants (highest index first)
   - Generates notifications for unassigned participants only (not for user-initiated assignment)
-- `RoomAssignmentService`: Unchanged - still auto-assigns when single room type selected
-- `ParticipantFieldOptionsProvider`: Unchanged - disables dropdown when single room type (auto-assigned)
+  - Handles missing field gracefully when single room type (field excluded from form)
+- `RoomAssignmentService`: Auto-assigns when single room type selected at DTO level
+- `CreateFieldStateProvider`: Hides `assignedRoomId` field when `SingleRoomTypeCondition` is true
+- `BookingDto::getSingleRoomLabel()`: Returns room label for template display when single room type
+- Template: Conditionally renders dropdown (multiple rooms) or read-only label (single room)
 
 **Example Scenario:**
 - User selects 1x "Doppelzimmer" (capacity 2), 3 participants
@@ -248,6 +252,13 @@ Critical for correct pricing and auto-reassignment:
 - `BulkInsuranceBookingCondition` hides dependent participant insurance fields
 - Uses `InsuranceService::batchAssignInsuranceToParticipants()` for price tier matching
 
+### Room Assignment Field
+- **Single room type**: Field completely hidden, room label displayed as read-only text
+- **Multiple room types**: Dropdown shown with all selected rooms from Step 1
+- `SingleRoomTypeCondition` controls field visibility in `CreateFieldStateProvider`
+- Auto-assignment by `RoomAssignmentService` happens at DTO level, independent of form field
+- Field handler gracefully handles missing field when excluded from form
+
 ## Data Flow
 
 ### Create Flow

src/Form/Model/BookingDto.php

@@ -151,6 +151,30 @@ class BookingDto
         return null !== $this->booking && 'O' === $this->booking->status;
     }
 
+    /**
+     * Gets the label of the single selected room type.
+     *
+     * Returns the room label when exactly one room type is selected (auto-assignment scenario).
+     * Used by templates to display the room assignment when the dropdown is hidden.
+     *
+     * @return string|null The room label or null if not a single room type scenario
+     */
+    public function getSingleRoomLabel(): ?string
+    {
+        $selectedRooms = $this->getSelectedRooms();
+
+        // Only return label when exactly one room type selected
+        if (1 !== count($selectedRooms)) {
+            return null;
+        }
+
+        $roomSelection = reset($selectedRooms);
+        $availableRooms = $this->travel->getAvailableRooms();
+        $room = $availableRooms[$roomSelection->roomId] ?? null;
+
+        return $room?->label;
+    }
+
     #[Assert\Callback(callback: 'validateRoomSelection', groups: ['booking_create_step_1'])]
     public function validateRoomSelection(ExecutionContextInterface $context): void
     {

src/Form/Service/CreateFieldStateProvider.php

@@ -205,9 +205,9 @@ class CreateFieldStateProvider extends AbstractFieldStateProvider
             'required' => new ApplicantCondition(),
         ];
 
-        // Make assignedRoomId readonly when only one room type is selected
+        // Hide assignedRoomId field when only one room type is selected (auto-assigned by RoomAssignmentService)
         $this->fieldStateConditions['assignedRoomId'] = [
-            'readonly' => new SingleRoomTypeCondition(),
+            'hidden' => new SingleRoomTypeCondition(),
         ];
 
         // Example field state conditions would be registered here

templates/booking/_participant_form.html.twig

@@ -85,14 +85,22 @@
 
             {# Room assignment #}
             <div class="grid grid-cols-2 gap-4">
-                {{ form_row(form.assignedRoomId, {
-                    'attr': {
-                        'hx-trigger': 'change',
-                        'hx-post': path(refreshRouteName, refreshRouteParams|default({index: participantIndex})),
-                        'hx-target': '#main-content',
-                        'hx-swap': 'innerHTML'
-                    }
-                }) }}
+                {% if form.assignedRoomId is defined %}
+                    {{ form_row(form.assignedRoomId, {
+                        'attr': {
+                            'hx-trigger': 'change',
+                            'hx-post': path(refreshRouteName, refreshRouteParams|default({index: participantIndex})),
+                            'hx-target': '#main-content',
+                            'hx-swap': 'innerHTML'
+                        }
+                    }) }}
+                {% else %}
+                    {# Display room label directly when only one room type selected (auto-assigned) #}
+                    <div>
+                        <label class="font-semibold mb-1 block">Zimmer</label>
+                        <div class="text-sm text-gray-600">{{ bookingDto.singleRoomLabel }}</div>
+                    </div>
+                {% endif %}
                 {% if form.remarksRoom is defined %}
                     {{ form_row(form.remarksRoom) }}
                 {% endif %}