feat(plating-migration): dry-run + Owner-approval workflow

Phase H of permissions overhaul (LAST subagent phase).

New models:
- fp.migration.preview (state: pending/approved/cancelled/rolled_back)
- fp.migration.preview.line (one per active internal user)

On -u, post_init_hook creates a preview in 'pending' state, walks all
active non-share users through the 12-rule mapping predicate chain
(first match wins, highest precedence first), and schedules a
mail.activity on every Owner.

Mapping table (per spec Section 5):
  uid 1/2 / Administrator   -> owner
  CGP DO (existing)          -> owner + res.company DO field set
  CGP Officer                -> quality_manager
  Manager / Shop Mgr (old)   -> manager
  Accounting                 -> manager
  Estimator-without-Manager  -> sales_rep (flagged: loses confirm)
  Supervisor / Receiving     -> shop_manager
  Operator                   -> technician
  catchall                   -> 'no'

Owner clicks 'Approve & Run' on the preview form -> sudo write removes
old plating groups, adds new role's group, posts Markup chatter audit.
Optionally sets res.company.x_fc_cgp_designated_official_id for the DO.

30-day rollback window via JSON snapshot of groups_id per line. Daily
cron (Fusion Plating: Purge Expired Role Migrations) clears snapshots
+ unlinks old [DEPRECATED] groups after 30 days.

ACL: fp.migration.preview + .line both Owner-only (CRUD).
Menu: Plating > Configuration > Role Migrations (Owner-only).

Tests cover: only-Owner-can-approve, approve advances state, cancel
blocks after approval, rollback restores groups_id, Estimator warning
flagged, uid 2 maps to owner, rollback blocked after 30 days.

Per CLAUDE.md: ir.cron uses only Odoo-19-valid fields (no numbercall,
no doall). Post-init hook is idempotent — won't double-create previews
or re-fire if all users already migrated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating/__manifest__.py

@@ -5,7 +5,7 @@
 
 {
     'name': 'Fusion Plating',
-    'version': '19.0.21.0.5',
+    'version': '19.0.21.0.6',
     'category': 'Manufacturing/Plating',
     'summary': 'Core plating / metal finishing ERP: facilities, processes, tanks, baths, jobs, operators.',
     'description': """
@@ -140,6 +140,12 @@ Copyright (c) 2026 Nexa Systems Inc. All rights reserved.
         # 'data/fp_recipe_anodize.xml',
         # 'data/fp_recipe_chem_conversion.xml',
         'data/fp_step_template_data.xml',
+        # Phase H — Owner-approval migration workflow.
+        # Views file declares the action + menu; cron declares the
+        # daily 30-day expiry purge. Both reference model_fp_migration_preview
+        # which Odoo's model autoload makes available before data load.
+        'views/fp_migration_views.xml',
+        'data/fp_migration_cron.xml',
     ],
     'post_init_hook': 'post_init_hook',
     'assets': {