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/models/fp_job.py

@@ -48,6 +48,17 @@ class FpJob(models.Model):
         'job_id',
         string='Recipe Overrides',
     )
+    # Phase 7 — migration idempotency key. Populated by
+    # scripts/migrate_to_fp_jobs.py to mark a fp.job as the mirror of a
+    # specific mrp.production. Used to skip already-migrated MOs on
+    # subsequent runs. Cleared after the 2-week shadow period.
+    legacy_mrp_production_id = fields.Integer(
+        string='Legacy MRP Production ID',
+        index=True,
+        help='Database id of the source mrp.production record this job '
+             'was migrated from. Used by the migration script for '
+             'idempotency. Cleared post-cutover.',
+    )
 
     # ------------------------------------------------------------------
     # Recipe → fp.job.step generation (Task 2.4)
@@ -485,3 +496,21 @@ class FpJob(models.Model):
             _logger.warning(
                 "Job %s: failed to auto-create cert: %s", self.name, e,
             )
+
+
+class FpJobStep(models.Model):
+    """Phase 7 — adds the migration idempotency key on fp.job.step.
+
+    Populated by scripts/migrate_to_fp_jobs.py to mark a step as the
+    mirror of a specific mrp.workorder. Used to skip already-migrated
+    WOs on subsequent runs.
+    """
+    _inherit = 'fp.job.step'
+
+    legacy_mrp_workorder_id = fields.Integer(
+        string='Legacy MRP Work Order ID',
+        index=True,
+        help='Database id of the source mrp.workorder this step was '
+             'migrated from. Used by the migration script for '
+             'idempotency. Cleared post-cutover.',
+    )