Add location tracking to weekend page

Weekend page now shows specific location (city and country) for each
Saturday and Sunday based on travel history:

- Analyzes flight arrivals and accommodation check-ins to determine exact location
- Shows "home" when at Bristol, UK
- Shows "City, 🏴 Country" format when traveling
- Handles multi-location trips by finding most recent travel within trip period
- Optimized to parse YAML files once instead of per-date lookup

Closes #191

🤖 Generated with [Claude Code](https://claude.ai/code)

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

templates/weekends.html

@@ -11,7 +11,9 @@
         <th class="text-end">Week</th>
         <th class="text-end">Date</th>
         <th>Saturday</th>
+        <th>Saturday Location</th>
         <th>Sunday</th>
+        <th>Sunday Location</th>
       </tr>
     </thead>
     <tbody>
@@ -43,6 +45,14 @@
           <strong>free</strong>
         {% endif %}
       </td>
+      {% if extra_class %}<td class="{{ extra_class|trim }}">{% else %}<td>{% endif %}
+        {% set city, country = weekend[day + '_location'] %}
+        {% if city == "Bristol" and country.alpha_2 | upper == "GB" %}
+          <strong>home</strong>
+        {% else %}
+          {{ city }}, {{ country.flag }} {{ country.name }}
+        {% endif %}
+      </td>
     {% endfor %}
     </tr>
   {% endfor %}