Add standalone trade calendar page with solar and lunar dates.

Move calendar from stats to /calendar nav page; show Gregorian and lunar on cells, month title, and day detail.

templates/base.html

@@ -89,6 +89,7 @@
                 {% if nav_items.ai %}<a href="{{ url_for('ai_messages_page') }}" class="{% if request.endpoint == 'ai_messages_page' %}active{% endif %}">AI 分析</a>{% endif %}
                 {% if nav_items.market %}<a href="{{ url_for('market_page') }}" class="{% if request.endpoint == 'market_page' %}active{% endif %}">行情K线</a>{% endif %}
                 <a href="{{ url_for('records') }}" class="{% if request.endpoint in ('records', 'trades') %}active{% endif %}">交易记录与复盘</a>
+                <a href="{{ url_for('trade_calendar') }}" class="{% if request.endpoint == 'trade_calendar' %}active{% endif %}">交易日历</a>
                 <a href="{{ url_for('stats') }}" class="{% if request.endpoint == 'stats' %}active{% endif %}">统计分析</a>
                 {% if nav_items.fees %}<a href="{{ url_for('fees') }}" class="{% if request.endpoint == 'fees' %}active{% endif %}">手续费配置</a>{% endif %}
                 <a href="{{ url_for('settings') }}" class="{% if request.endpoint == 'settings' %}active{% endif %}">系统设置</a>