Implement Schengen Area Compliance Report

How many close am I to 90 days in the last 180.

Fixes #193.

templates/macros.html

@@ -351,6 +351,18 @@
       <div>Total CO₂: {{ "{:,.1f}".format(total_co2_kg) }} kg</div>
     {% endif %}
 
+    {% if trip.schengen_compliance %}
+      <div>
+        <strong>Schengen:</strong>
+        {% if trip.schengen_compliance.is_compliant %}
+          <span class="badge bg-success">✅ Compliant</span>
+        {% else %}
+          <span class="badge bg-danger">❌ Non-compliant</span>
+        {% endif %}
+        <span class="text-muted small">({{ trip.schengen_compliance.total_days_used }}/90 days used)</span>
+      </div>
+    {% endif %}
+
     {{ conference_list(trip) }}
 
     {% for day, elements in trip.elements_grouped_by_day() %}