fix(data): restore pagination early-break + update test count

Code review on b977c37 flagged: with dataset smaller than limit=1000
(typical Phase 1 case), the loop made an extra HTTP request that
returned duplicate rows. Restored `if len(rows) < limit: break`
after extending. Test assertion adjusted from 2 to 1 calls.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/test_ohlcv_loader.py

@@ -55,7 +55,7 @@ def test_loader_uses_cache_on_second_call(tmp_path: Path, mocker, sample_ohlcv_r
     df1 = loader.load(req)
     df2 = loader.load(req)
 
-    assert fake_exchange.fetch_ohlcv.call_count == 2  # paginazione interna, non caching
+    assert fake_exchange.fetch_ohlcv.call_count == 1  # 48 < limit, single batch
     pd.testing.assert_frame_equal(df1, df2)
     # Seconda chiamata legge da cache, non chiama exchange
     fake_exchange.fetch_ohlcv.reset_mock()