Add FXMacroData macro data helpers

[roberttidball]

Summary

• add efinance.macro DataFrame helpers for FXMacroData catalogue, indicator history, release calendar, latest announcements, predictions, FX, COT, commodities, and market sessions
• expose the macro module through the existing top-level efinance imports
• document API reference and examples with public USD/no-key usage plus optional FXMD_API_KEY / FXMACRODATA_API_KEY environment keys

FXMacroData coverage

Capability	efinance surface	Status
Discovery/catalogue	ef.macro.get_data_catalogue	Native DataFrame helper
Macro indicator history	ef.macro.get_indicator	Native DataFrame helper
Release calendar	ef.macro.get_calendar	Native DataFrame helper
Event predictions	ef.macro.get_predictions	Native DataFrame helper
FX spot history	ef.macro.get_forex	Native DataFrame helper
FX market sessions	ef.macro.get_market_sessions	Native DataFrame helper
COT positioning	ef.macro.get_cot	Native DataFrame helper
Commodities	ef.macro.get_commodities	Native DataFrame helper

Validation

• python -m py_compile efinance\\macro\\getter.py efinance\\macro\\__init__.py efinance\\api\\__init__.py efinance\\__init__.py
• python -c "import efinance as ef; print(ef.macro.get_calendar('usd').head(1).shape); print(ef.macro.get_data_catalogue('usd').head(1).shape)"
• git diff --check