Add multi-station support, GWR fares API, and Circle line improvements

- Support any station with direct trains to Paddington; station CRS code
  is now part of the URL (/results/<crs>/<slug>/<date>)
- Load station list from data/direct_to_paddington.tsv; show dropdown on
  index page; 404 for unknown station codes
- Fetch live GWR walk-on fares via api.gwr.com for all stations (SSS/SVS/SDS
  with restrictions already applied per train); cache 30 days
- Scrape Paddington arrival platform numbers from RTT
- Show unreachable morning Eurostars (before first reachable service only)
- Circle line: show actual KX St Pancras arrival times (not check-in estimate)
  and add a second backup service in the transfer column
- Widen page max-width to 1100px for longer station names

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/index.html

@@ -3,12 +3,13 @@
 <div class="card">
   <h2>Plan your journey</h2>
   <form method="get" action="{{ url_for('search') }}">
-    <div class="form-group">
-      <span class="field-label">Departure point</span>
-      <div class="fixed-station" aria-label="Departure point">
-        <strong>Bristol Temple Meads</strong>
-        <span>Fixed starting station for all journeys</span>
-      </div>
+    <div class="form-group-lg">
+      <label for="station_crs" class="field-label">Departure point</label>
+      <select id="station_crs" name="station_crs" class="form-control">
+        {% for name, crs in stations %}
+          <option value="{{ crs }}" {% if crs == 'BRI' %}selected{% endif %}>{{ name }} ({{ crs }})</option>
+        {% endfor %}
+      </select>
     </div>
 
     <div class="form-group">