feat: add the booking board with floor plan and calendar

templates/booking/_modal_create.html.twig

@@ -0,0 +1,40 @@
+{#
+    The booking modal. Extending htmx_modal.html.twig keeps it a standalone fragment -- it is a
+    valid response on its own, which is what the opener's hx-swap="beforeend" onto <body> needs.
+
+    The form targets the modal itself with outerHTML, which does double duty:
+      * invalid submit -> Symfony returns 422, htmx swaps it (see responseHandling in app.js) and
+        the modal replaces itself with the errors showing;
+      * success -> the response is nothing but out-of-band board blocks, so the modal is replaced
+        with an empty fragment, i.e. it closes.
+#}
+{% extends 'htmx_modal.html.twig' %}
+
+{% block title %}{{ resource.label }} buchen{% endblock %}
+
+{% block content %}
+    {{ form_start(form, { attr: {
+        'hx-post': form.vars.action,
+        'hx-target': '#htmx-modal',
+        'hx-swap': 'outerHTML',
+    } }) }}
+        {# Root-level errors, which is where a rejected booking lands -- form_end/form_rest does
+           NOT render these, so leaving this out makes the 422 path silently blank. #}
+        {{ form_errors(form) }}
+
+        <p class="pb-4 text-sm text-gray-500">
+            {{ resource.type.label }} · {{ resource.label }}
+        </p>
+
+        {{ form_row(form.date) }}
+
+        <div class="flex justify-end gap-2 pt-6">
+            <button type="button" class="button button--neutral" {{ stimulus_action('modal', 'close') }}>
+                Abbrechen
+            </button>
+            <button type="submit" class="button button--primary">
+                Buchen
+            </button>
+        </div>
+    {{ form_end(form) }}
+{% endblock %}