feat(sub12b): fp.rack.tag — rack-label registry + 4 starter tags

M2M tag registry: Rush / Hold for QC / Damaged / Customer Sample.
Each rack can carry many tags; tags surface as coloured chips on the
plant-overview rack rows + Move Rack dialog (Task 13).

Plating → Configuration → Rack Tags menu (sequence 48).
post_init_hook seeds 4 starters — idempotent (no-op if any exist).

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

fusion_plating/fusion_plating/models/__init__.py

@@ -37,3 +37,6 @@ from . import fp_process_node_inherit
 from . import fp_step_template
 from . import fp_step_template_input
 from . import fp_step_template_transition_input
+
+# Sub 12b — Rack-aware moves + persistent labor reconciliation
+from . import fp_rack_tag

fusion_plating/fusion_plating/models/fp_rack_tag.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+# Part of the Fusion Plating product family.
+
+from odoo import fields, models
+
+
+class FpRackTag(models.Model):
+    """Operator-visible labels applied to physical racks.
+
+    "Rush" / "Hold for QC" / "Customer-Amphenol" / "Damaged" — the
+    coloured tag chips that appear in the Move Rack dialog and on the
+    plant-overview rack rows. M2M; one rack can carry many tags.
+    """
+    _name = 'fp.rack.tag'
+    _description = 'Fusion Plating — Rack Tag'
+    _order = 'sequence, name'
+
+    name = fields.Char(string='Tag', required=True, translate=True)
+    color = fields.Integer(string='Color')
+    sequence = fields.Integer(string='Sequence', default=10)
+    active = fields.Boolean(string='Active', default=True)
+    company_id = fields.Many2one(
+        'res.company', string='Company',
+        default=lambda self: self.env.company,
+    )
+
+    _sql_constraints = [
+        ('fp_rack_tag_name_company_uniq',
+         'unique(name, company_id)',
+         'Rack tag name must be unique within a company.'),
+    ]