Add timeline car import and CO2 trip stats

tests/test_trip_stats.py

@@ -3,6 +3,7 @@
 from datetime import date
 
 import agenda
+import pytest
 from agenda.stats import calculate_yearly_stats
 from agenda.types import Trip
 
@@ -35,3 +36,22 @@ def test_new_country_respects_previously_visited() -> None:
 
     yearly_stats = calculate_yearly_stats(trips, {"CZ"})
     assert "new_countries" not in yearly_stats[2024]
+
+
+def test_yearly_stats_tracks_co2_by_transport_type() -> None:
+    """CO₂ stats should include a per-transport-type breakdown."""
+    trip = Trip(
+        start=date(2024, 5, 1),
+        travel=[
+            {"type": "car", "distance": 100.0, "co2_kg": 21.8},
+            {"type": "bus", "distance": 50.0, "co2_kg": 5.0},
+        ],
+    )
+
+    yearly_stats = calculate_yearly_stats([trip])
+
+    assert yearly_stats[2024]["co2_kg"] == pytest.approx(26.8)
+    assert yearly_stats[2024]["co2_by_transport_type"] == {
+        "car": 21.8,
+        "bus": 5.0,
+    }