Show cheapest GWR fare per journey and flag unreachable morning Eurostars

Add cheapest_gwr_ticket() to trip_planner.py encoding the SSS/SVS/SDS
walk-on single restrictions for Bristol Temple Meads → Paddington: on
weekdays, Super Off-Peak (£45) is valid before 05:05 or from 09:58,
Off-Peak (£63.60) from 08:26, and Anytime (£138.70) covers the gap.
Weekends have no restrictions. The fare is included in each trip dict
and displayed in a new GWR Fare column on the results page.

Also wire up find_unreachable_morning_eurostars() into the results view
so early Eurostar services unreachable from Bristol appear in the table,
with tests covering both features.

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

app.py

@@ -7,7 +7,7 @@ from datetime import date, timedelta
 from cache import get_cached, set_cached
 import scraper.eurostar as eurostar_scraper
 import scraper.realtime_trains as rtt_scraper
-from trip_planner import combine_trips
+from trip_planner import combine_trips, find_unreachable_morning_eurostars
 
 RTT_PADDINGTON_URL = (
     "https://www.realtimetrains.co.uk/search/detailed/"
@@ -109,6 +109,18 @@ def results(slug, travel_date):
             error = f"{error}; {msg}" if error else msg
 
     trips = combine_trips(gwr_trains, eurostar_trains, travel_date, min_connection, max_connection)
+    unreachable_morning_services = find_unreachable_morning_eurostars(
+        gwr_trains,
+        eurostar_trains,
+        travel_date,
+        min_connection,
+        max_connection,
+    )
+    result_rows = sorted(
+        [{'row_type': 'trip', **trip} for trip in trips]
+        + [{'row_type': 'unreachable', **service} for service in unreachable_morning_services],
+        key=lambda row: row['depart_st_pancras'],
+    )
 
     dt = date.fromisoformat(travel_date)
     prev_date = (dt - timedelta(days=1)).isoformat()
@@ -121,6 +133,8 @@ def results(slug, travel_date):
     return render_template(
         'results.html',
         trips=trips,
+        result_rows=result_rows,
+        unreachable_morning_services=unreachable_morning_services,
         destinations=DESTINATIONS,
         destination=destination,
         travel_date=travel_date,