Adds _fc_retention_gc() that deletes rows older than the configured
horizon (default 365 days; 0 = keep forever). Registered as a daily
ir.cron. Tests verify both the delete path and the "keep forever"
short-circuit.
Also documents the Odoo 19 gotcha that ir.cron dropped the numbercall
field (the legacy "-1 = run forever" pattern now raises ValueError at
install time; just omit the field).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
1b8038d8e8