feat(growth): same-day 1-day baselines for new videos

Let 1-day view growth use a zero baseline for videos published today, and the first successful sample for older videos ingested today, without mixing those into 7/30-day rankings.

tests/test_analytics.py

@@ -131,6 +131,18 @@ def test_compute_growth():
     no_gap = compute_growth(100, 90, 0)
     assert no_gap.available is False
 
+    same_day = compute_growth(100, 90, 0, allow_zero_gap=True)
+    assert same_day.available is True
+    assert same_day.delta == 10
+    assert same_day.per_day is None
+    assert same_day.gap_days == 0
+    assert abs(same_day.rate - 10 / 90) < 1e-12
+
+    from_zero_same_day = compute_growth(50, 0, 0, allow_zero_gap=True)
+    assert from_zero_same_day.delta == 50
+    assert from_zero_same_day.rate == 50.0
+    assert from_zero_same_day.per_day is None
+
     growth = compute_growth(1000, 800, 7)
     assert growth.available is True
     assert growth.delta == 200