Persist best efforts during import and add resumable backfill

tests/test_records.py

@@ -3,16 +3,18 @@ from types import SimpleNamespace
 
 import pytest
 
-from app.records import best_efforts, record_book
+from app.records import best_efforts, persist_efforts, record_book
 
 
 def run(points, id=1, sport="running"):
-    return SimpleNamespace(
+    activity = SimpleNamespace(
         id=id,
         sport=sport,
         started_at=datetime(2026, 1, 1, tzinfo=UTC) + timedelta(days=id),
         samples=[{"distance": d, "time": t} for d, t in points],
     )
+    persist_efforts(activity)
+    return activity
 
 
 def test_fastest_window_can_start_between_samples():