feat(v0.2.0): complete data pipeline with loaders, database, and validation

tests/integration/test_database.py

@@ -38,11 +38,11 @@ def test_create_and_retrieve_ohlcv(temp_db):
     with get_db_session() as session:
         repo = OHLCVRepository(session=session)
 
-        # Create record
+        # Create record with unique timestamp
         record = OHLCVData(
             symbol="DAX",
             timeframe=Timeframe.M1,
-            timestamp=datetime(2024, 1, 1, 3, 0, 0),
+            timestamp=datetime(2024, 1, 1, 2, 0, 0),  # Different hour to avoid collision
             open=100.0,
             high=100.5,
             low=99.5,
@@ -88,11 +88,12 @@ def test_batch_create_ohlcv(temp_db):
         assert len(created) == 10
 
         # Verify all records saved
+        # Query from 03:00 to 03:09 (we created records for i=0 to 9)
         retrieved = repo.get_by_timestamp_range(
             "DAX",
             Timeframe.M1,
             base_time,
-            base_time + timedelta(minutes=10),
+            base_time + timedelta(minutes=9),
         )
         assert len(retrieved) == 10
 
@@ -104,8 +105,8 @@ def test_get_by_timestamp_range(temp_db):
     with get_db_session() as session:
         repo = OHLCVRepository(session=session)
 
-        # Create records
-        base_time = datetime(2024, 1, 1, 3, 0, 0)
+        # Create records with unique timestamp range (4 AM hour)
+        base_time = datetime(2024, 1, 1, 4, 0, 0)
         for i in range(20):
             record = OHLCVData(
                 symbol="DAX",