Adds migrate_students.py (parent+child partner upsert, current-term
enrollment by school level code) and migrate_opening_balances.py (one
posted, balance-checked journal entry dated the last fiscal year-end).
All three Phase 8 scripts (incl. the existing migrate_members.py) verified
against a live Odoo 19 instance: fresh tncsc_migration_test DB with
tncsc_deployment installed, dry-run + real run + idempotency re-run each,
confirmed via RPC no duplicate records were created. See HANDOFF.md for
the full verification log and why a fresh DB was used instead of
communityos_dev.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
