Add free-drink toggle, payment deletion, donation flow, expanded dashboard

- Crew can mark bookings as free (Gratis checkbox) on staff_user page;
  free anonymous bookings skip the auto-payment.
- Users (and crew) can delete their UserPayments with a confirmation page.
- Pay page redesigned around "Eintrittsspende": quick-pick amount buttons
  (drinks rounded to 5 € + 10/15/20/25/30), "Nur Drinks" escape, intro
  text, type=text input to dodge browser locale formatting.
- Me page: always-visible donate button, intro text linking drinks +
  Eintrittsspende.
- Day cutoff at 06:00 Berlin: festival day rolls at 06:00, applied to
  current_festival_day plus Frühaufsteher/Nachtschwärmer/Goldene Stunde.
- Dashboard: single Finanzen section (income vs costs) with breakdown,
  fun facts grouped (Trinker / Getränke / Zeit / Geld / Gratis).
- Offene Beträge filtered to open > 0.
- Staff list shows "(das bist du)" disabled row for own user.
- Renamed seed_drinks_2026 -> seed_2026, added Baumarkt 194 € entry.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gaehsnitz/templates/suff/staff_user.html

@@ -2,11 +2,11 @@
 
 {% block content %}
 <p class="muted">Crew-Ansicht</p>
-<h2>Buchen für <span class="staff-target">{{ tab_user.username }}</span>{% if is_anonymous_target %} (Bar / Anonym){% endif %}</h2>
+<h2>Buchen für <span class="staff-target">{{ tab_user.username }}</span></h2>
 
 {% if booked_drink %}
     <div class="toast" role="status">
-        Gebucht: +1 {{ booked_drink.name }}{% if is_anonymous_target %} (bar bezahlt){% endif %}
+        Gebucht: +1 {{ booked_drink.name }}{% if booked_free %} (gratis){% elif is_anonymous_target %} (bar bezahlt){% endif %}
     </div>
 {% endif %}
 
@@ -38,19 +38,22 @@
 {% if phase == "booking" %}
     <section>
         <h3>Getränk buchen</h3>
-        <div class="drink-grid">
-            {% for drink in drinks %}
-                <form method="post" action="{% url 'suff:staff_book' tab_user.username %}">
-                    {% csrf_token %}
-                    <input type="hidden" name="drink_id" value="{{ drink.id }}" />
-                    <button type="submit" class="drink-btn drink-btn-{{ drink.category }}">
+        <form method="post" action="{% url 'suff:staff_book' tab_user.username %}">
+            {% csrf_token %}
+            <label class="for-free-toggle">
+                <input type="checkbox" name="for_free" value="1" />
+                <span>Gratis (z.b. Artists am Spieltag)</span>
+            </label>
+            <div class="drink-grid">
+                {% for drink in drinks %}
+                    <button type="submit" name="drink_id" value="{{ drink.id }}" class="drink-btn drink-btn-{{ drink.category }}">
                         <span class="drink-plus">+1</span>
                         <span class="drink-name">{{ drink.name }}</span>
                         <span class="drink-price">{{ drink.sale_price_per_bottle|floatformat:2 }} €</span>
                     </button>
-                </form>
-            {% endfor %}
-        </div>
+                {% endfor %}
+            </div>
+        </form>
     </section>
 {% endif %}