feat: implement date range support with period metrics in results endpoint

- Replace deprecated `date` parameter with `start_date`/`end_date`
- Return single-date format (detailed) when dates are equal
- Return range format (lightweight with period metrics) when dates differ
- Add period metrics: period_return_pct, annualized_return_pct, calendar_days, trading_days
- Default to last 30 days when no dates provided
- Group results by model for date range queries
- Add comprehensive test coverage for both response formats
- Implement automatic edge trimming for date ranges
- Add 404 error handling for empty result sets
- Include 422 error for deprecated `date` parameter usage

tests/api/test_results_v2.py

@@ -1,8 +1,12 @@
 """Tests for results_v2 endpoint date validation."""
 
 import pytest
+import json
 from datetime import datetime, timedelta
+from fastapi.testclient import TestClient
 from api.routes.results_v2 import validate_and_resolve_dates
+from api.main import create_app
+from api.database import Database
 
 
 def test_validate_no_dates_provided():
@@ -59,3 +63,160 @@ def test_validate_future_date():
 
     with pytest.raises(ValueError, match="Cannot query future dates"):
         validate_and_resolve_dates(future, future)
+
+
+@pytest.fixture
+def test_db(tmp_path):
+    """Create test database with sample data."""
+    db_path = str(tmp_path / "test.db")
+    db = Database(db_path)
+
+    # Create a job first (required by foreign key constraint)
+    db.connection.execute(
+        """
+        INSERT INTO jobs (job_id, config_path, date_range, models, status, created_at)
+        VALUES (?, ?, ?, ?, ?, datetime('now'))
+        """,
+        ("test-job-1", "config.json", '["2024-01-16", "2024-01-17"]', '["gpt-4"]', "completed")
+    )
+    db.connection.commit()
+
+    # Create sample trading days (use dates in the past)
+    trading_day_id_1 = db.create_trading_day(
+        job_id="test-job-1",
+        model="gpt-4",
+        date="2024-01-16",
+        starting_cash=10000.0,
+        starting_portfolio_value=10000.0,
+        daily_profit=0.0,
+        daily_return_pct=0.0,
+        ending_cash=9500.0,
+        ending_portfolio_value=10100.0,
+        reasoning_summary="Bought AAPL",
+        total_actions=1,
+        session_duration_seconds=45.2,
+        days_since_last_trading=0
+    )
+
+    db.create_holding(trading_day_id_1, "AAPL", 10)
+    db.create_action(trading_day_id_1, "buy", "AAPL", 10, 150.0)
+
+    trading_day_id_2 = db.create_trading_day(
+        job_id="test-job-1",
+        model="gpt-4",
+        date="2024-01-17",
+        starting_cash=9500.0,
+        starting_portfolio_value=10100.0,
+        daily_profit=100.0,
+        daily_return_pct=1.0,
+        ending_cash=9500.0,
+        ending_portfolio_value=10250.0,
+        reasoning_summary="Held AAPL",
+        total_actions=0,
+        session_duration_seconds=30.0,
+        days_since_last_trading=1
+    )
+
+    db.create_holding(trading_day_id_2, "AAPL", 10)
+
+    return db
+
+
+def test_get_results_single_date(test_db):
+    """Test single date query returns detailed format."""
+    app = create_app(db_path=test_db.db_path)
+    app.state.test_mode = True
+
+    # Override the database dependency to use our test database
+    from api.routes.results_v2 import get_database
+
+    def override_get_database():
+        return test_db
+
+    app.dependency_overrides[get_database] = override_get_database
+
+    client = TestClient(app)
+
+    response = client.get("/results?start_date=2024-01-16&end_date=2024-01-16")
+
+    assert response.status_code == 200
+    data = response.json()
+
+    assert data["count"] == 1
+    assert len(data["results"]) == 1
+
+    result = data["results"][0]
+    assert result["date"] == "2024-01-16"
+    assert result["model"] == "gpt-4"
+    assert "starting_position" in result
+    assert "daily_metrics" in result
+    assert "trades" in result
+    assert "final_position" in result
+
+
+def test_get_results_date_range(test_db):
+    """Test date range query returns metrics format."""
+    app = create_app(db_path=test_db.db_path)
+    app.state.test_mode = True
+
+    # Override the database dependency to use our test database
+    from api.routes.results_v2 import get_database
+
+    def override_get_database():
+        return test_db
+
+    app.dependency_overrides[get_database] = override_get_database
+
+    client = TestClient(app)
+
+    response = client.get("/results?start_date=2024-01-16&end_date=2024-01-17")
+
+    assert response.status_code == 200
+    data = response.json()
+
+    assert data["count"] == 1
+    assert len(data["results"]) == 1
+
+    result = data["results"][0]
+    assert result["model"] == "gpt-4"
+    assert result["start_date"] == "2024-01-16"
+    assert result["end_date"] == "2024-01-17"
+    assert "daily_portfolio_values" in result
+    assert "period_metrics" in result
+
+    # Check daily values
+    daily_values = result["daily_portfolio_values"]
+    assert len(daily_values) == 2
+    assert daily_values[0]["date"] == "2024-01-16"
+    assert daily_values[0]["portfolio_value"] == 10100.0
+    assert daily_values[1]["date"] == "2024-01-17"
+    assert daily_values[1]["portfolio_value"] == 10250.0
+
+    # Check period metrics
+    metrics = result["period_metrics"]
+    assert metrics["starting_portfolio_value"] == 10000.0
+    assert metrics["ending_portfolio_value"] == 10250.0
+    assert metrics["period_return_pct"] == 2.5
+    assert metrics["calendar_days"] == 2
+    assert metrics["trading_days"] == 2
+
+
+def test_get_results_empty_404(test_db):
+    """Test 404 when no data matches filters."""
+    app = create_app(db_path=test_db.db_path)
+    app.state.test_mode = True
+
+    # Override the database dependency to use our test database
+    from api.routes.results_v2 import get_database
+
+    def override_get_database():
+        return test_db
+
+    app.dependency_overrides[get_database] = override_get_database
+
+    client = TestClient(app)
+
+    response = client.get("/results?start_date=2024-02-01&end_date=2024-02-05")
+
+    assert response.status_code == 404
+    assert "No trading data found" in response.json()["detail"]