Fix CSV OHLCV based tests (#331)

[MDUYN]

Summary

Adds comprehensive test coverage for CSV data providers and introduces the new CSVTickerDataProvider class.

Closes #331

Changes

New: CSVTickerDataProvider

• New data provider class that loads ticker data from OHLCV CSV files
• Maps OHLCV columns to ticker dict format (bid, ask, last derived from Close)
• Supports has_data(), get_data(), backtest mode, and the copy pattern
• Exported at all package levels (__init__.py chain)

New Tests: CSVOHLCVDataProvider (19 tests)

• Basic data loading and column validation
• has_data() with matching/mismatched symbol, market, time_frame
• has_data() with no dates, out-of-range end date, window_size
• get_data() with start_date and end_date
• Backtest mode: prepare_backtest_data() and get_backtest_data()
• Invalid backtest ranges (start before data, end after data)
• Custom identifier, market, and symbol properties

New Tests: CSVTickerDataProvider (7 tests)

• Basic loading
• has_data() with matching/mismatched symbol, market, data_type
• get_data() returns correct ticker dict with expected keys
• Custom identifier support

Other

• Added test data CSV files for backtesting scenarios
• Fixed test_trade_price_update.py data fixtures
• All 29 CSV provider tests passing, 0 flake8 lint issues