Add price emoji indicators and hover text to results table

Show 💰 on total prices within £10 of the cheapest journey and 💸
within £10 of the most expensive, mirroring the ⚡/🐢 logic for journey
time. Only applied when more than one priced trip exists.

Add title attributes to ⚠️ ("Tight connection"), ⚡ ("Fastest journey"),
and 🐢 ("Slowest journey") for accessibility and discoverability.

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

tests/test_app.py

@@ -155,8 +155,8 @@ def test_results_marks_trips_within_five_minutes_of_fastest_and_slowest(monkeypa
     html = resp.get_data(as_text=True)
 
     assert resp.status_code == 200
-    assert html.count('title="Fastest option"') == 2
-    assert html.count('title="Slowest option"') == 2
+    assert html.count('title="Fastest journey"') == 2
+    assert html.count('title="Slowest journey"') == 2
     assert '4h 50m ⚡' in html
     assert '4h 55m ⚡' in html
     assert '5h 20m 🐢' in html