feat: add cards view to calendar with 2-column grid layout

New "Karty" view shows up to 8 upcoming events as dark gradient cards
in a 2-column grid, matching the homepage event banner style.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/calendar/index.html

@@ -549,6 +549,110 @@
             font-size: var(--font-size-xl);
         }
     }
+
+    /* ===== WIDOK KART ===== */
+    .cards-grid {
+        display: grid;
+        grid-template-columns: repeat(2, 1fr);
+        gap: var(--spacing-md);
+    }
+
+    .card-banner {
+        background: linear-gradient(135deg, #1e3050 0%, #2E4872 100%);
+        border-radius: var(--radius-lg);
+        padding: var(--spacing-md);
+        color: white;
+        display: flex;
+        flex-direction: column;
+        gap: var(--spacing-sm);
+        box-shadow: var(--shadow-md);
+        position: relative;
+        overflow: hidden;
+        text-decoration: none;
+        transition: var(--transition);
+    }
+
+    .card-banner:hover {
+        transform: translateY(-2px);
+        box-shadow: 0 10px 30px rgba(46, 72, 114, 0.25);
+        filter: brightness(1.05);
+    }
+
+    .card-banner::before {
+        content: '';
+        position: absolute;
+        top: -50%;
+        right: -10%;
+        width: 200px;
+        height: 200px;
+        background: rgba(255,255,255,0.06);
+        border-radius: 50%;
+    }
+
+    .card-banner.external {
+        background: linear-gradient(135deg, #334155 0%, #475569 100%);
+    }
+
+    .card-banner-title {
+        font-size: var(--font-size-base);
+        font-weight: 700;
+        line-height: 1.3;
+    }
+
+    .card-banner-meta {
+        font-size: var(--font-size-xs);
+        opacity: 0.9;
+        display: flex;
+        flex-wrap: wrap;
+        gap: var(--spacing-sm);
+    }
+
+    .card-banner-bottom {
+        display: flex;
+        align-items: center;
+        justify-content: space-between;
+        gap: var(--spacing-sm);
+        margin-top: auto;
+    }
+
+    .card-banner-attendees {
+        display: flex;
+        align-items: center;
+        gap: var(--spacing-xs);
+        background: rgba(255,255,255,0.15);
+        padding: var(--spacing-xs) var(--spacing-sm);
+        border-radius: var(--radius);
+        font-weight: 600;
+        font-size: var(--font-size-xs);
+    }
+
+    .card-banner .btn-card {
+        background: white;
+        color: #2E4872;
+        border: none;
+        padding: var(--spacing-xs) var(--spacing-md);
+        font-weight: 600;
+        font-size: var(--font-size-sm);
+        border-radius: var(--radius-btn);
+        text-decoration: none;
+        cursor: pointer;
+        transition: var(--transition);
+    }
+
+    .card-banner .btn-card:hover {
+        background: #EDF0F5;
+    }
+
+    .card-banner .btn-card-registered {
+        background: #166534;
+        color: white;
+    }
+
+    @media (max-width: 768px) {
+        .cards-grid {
+            grid-template-columns: 1fr;
+        }
+    }
 </style>
 {% endblock %}
 
@@ -625,6 +729,9 @@
         <a href="?view=list" class="{% if view_mode == 'list' %}active{% endif %}">
             Lista
         </a>
+        <a href="?view=cards" class="{% if view_mode == 'cards' %}active{% endif %}">
+            Karty
+        </a>
         <a href="?view=grid&year={{ year }}&month={{ month }}" class="{% if view_mode == 'grid' %}active{% endif %}">
             Kalendarz
         </a>
@@ -713,6 +820,60 @@
     <span><span class="badge-type external">Zewnętrzne</span></span>
 </div>
 
+{% elif view_mode == 'cards' %}
+<!-- ================ WIDOK KART ================ -->
+
+<div class="events-section">
+    <h2>Nadchodzące wydarzenia</h2>
+
+    {% if upcoming_events %}
+    <div class="cards-grid">
+        {% for event in upcoming_events[:8] %}
+        <a href="{{ url_for('calendar.calendar_event', event_id=event.id) }}" class="card-banner{% if event.is_external %} external{% endif %}">
+            <div class="card-banner-title">
+                {{ event.title }} →
+                {% if event.is_external and event.external_source %}
+                <span style="display:inline-block; background:rgba(255,255,255,0.2); color:#fff; font-size:10px; padding:2px 6px; border-radius:4px; font-weight:600; vertical-align:middle; margin-left:4px;">🌐 {{ event.external_source }}</span>
+                {% endif %}
+            </div>
+            <div class="card-banner-meta">
+                <span>📆 {{ event.event_date.strftime('%d.%m.%Y') }} ({{ ['Pon', 'Wt', 'Śr', 'Czw', 'Pt', 'Sob', 'Nd'][event.event_date.weekday()] }})</span>
+                {% if event.time_start %}
+                <span>🕕 {{ event.time_start.strftime('%H:%M') }}</span>
+                {% endif %}
+                {% if event.location %}
+                <span>📍 {{ event.location[:30] }}{% if event.location|length > 30 %}...{% endif %}</span>
+                {% endif %}
+            </div>
+            <div class="card-banner-bottom">
+                <div class="card-banner-attendees">
+                    👥 Zapisanych: {{ event.total_attendee_count }} {% if event.total_attendee_count == 1 %}osoba{% elif event.total_attendee_count in [2,3,4] %}osoby{% else %}osób{% endif %}
+                </div>
+                <div>
+                    {% set is_attending = event.attendees|selectattr('user_id','equalto',current_user.id)|list %}
+                    {% if is_attending %}
+                    <span class="btn-card btn-card-registered">✓ Zapisany/a</span>
+                    {% else %}
+                    <span class="btn-card">Zapisz się →</span>
+                    {% endif %}
+                </div>
+            </div>
+        </a>
+        {% endfor %}
+    </div>
+
+    {% if upcoming_events|length > 8 %}
+    <div style="text-align: center; margin-top: var(--spacing-lg);">
+        <a href="?view=list" class="btn btn-outline">Zobacz wszystkie ({{ upcoming_events|length }}) →</a>
+    </div>
+    {% endif %}
+    {% else %}
+    <div class="empty-state">
+        <p>Brak nadchodzących wydarzeń</p>
+    </div>
+    {% endif %}
+</div>
+
 {% else %}
 <!-- ================ WIDOK LISTY ================ -->