Pure-Python helper for FX conversion at report end-date. Handles direct
rates, inverse rates, and fallback to most-recent-rate-on-or-before.
fetch_rates() pulls from res.currency.rate using the same
1/rate inversion convention Odoo uses internally.
Made-with: Cursor
Three service modules with no Odoo dependencies:
- date_periods: fiscal year/month/quarter bounds + comparison derivation
- account_hierarchy: parent-child tree walker with type filtering
- totaling: move-line aggregation primitives
18 unit tests covering edge cases (December rollover, Feb 29, fiscal-
year-before-start, balance check tolerance).
Made-with: Cursor