Add FXMacroData bar source

[roberttidball]

Summary

Adds a direct FXMacroData daily bar source under basana.external.fxmacrodata.bars.

The new BarSource:

• fetches https://fxmacrodata.com/api/v1/forex/{base}/{quote} with start_date and end_date
• supports API keys via constructor, FXMACRODATA_API_KEY, or FXMD_API_KEY
• converts FXMacroData daily spot/reference rows into close-only BarEvents where open/high/low/close are equal and volume is 0
• sorts emitted events by timestamp for dispatcher consumption

This is intended for FX and macro research/backtesting where daily official-source reference rates are useful, not for intraday exchange-traded candles.

Validation

• python -m pytest tests\test_fxmacrodata_bars.py -q
• python -m ruff check basana\external\fxmacrodata tests\test_fxmacrodata_bars.py
• python -m compileall -q basana\external\fxmacrodata
• git diff --check