feat(jobs): Phase 7 — migration script + legacy id fields

Adds legacy_mrp_production_id (Integer index) on fp.job and
legacy_mrp_workorder_id on fp.job.step. Used as the idempotency
key during cutover migration.

Three scripts under fusion_plating_jobs/scripts/:
- audit_pre_migration.py   — counts and data-quality concerns BEFORE
- migrate_to_fp_jobs.py    — copies MO->fp.job, WO->fp.job.step, time
                             logs, rebinds cross-refs (batches,
                             holds, certs, readings, portals,
                             inspections, deliveries). Idempotent.
- audit_post_migration.py  — counts and verifies AFTER

Migration is run manually from \`odoo shell\` at cutover (not as
auto post-migration hook, for safety). README explains usage.

Tests verify the legacy id fields exist and the migration script
files are well-formed Python.

Manifest 19.0.1.9.0 -> 19.0.2.0.0.

Part of: native job model migration (spec 2026-04-25)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_jobs/__manifest__.py

@@ -3,7 +3,7 @@
 # License OPL-1 (Odoo Proprietary License v1.0)
 {
     'name': 'Fusion Plating — Native Jobs',
-    'version': '19.0.1.9.0',
+    'version': '19.0.2.0.0',
     'category': 'Manufacturing/Plating',
     'summary': 'Native plating job model — replaces mrp.production / mrp.workorder bridge.',
     'description': """