feat(fusion_plating): box-level tracking (fp.box) + thermal job-sticker redesign

Box registry: new fp.box model (fusion_plating_receiving), one record per
received box, auto-created when a receiving is marked Counted (idempotent
_fp_sync_boxes — grows/shrinks with box_count_in, never touches an advanced
box). Status received -> racked -> in_process -> packed -> shipped, per-box
scannable QR (/fp/box/<id> controller). Backfill migration for receivings
counted before tracking shipped. Boxes list/kanban/form + receiving smart
button.

Job stickers redesigned (thermal label, 6x4 in / 152x102mm, mm layout @
paperformat dpi=96 so mm maps 1:1 in wkhtmltopdf — see rule 14):
- Internal Job Sticker = Layout A, ONE per job (shop notes from
  x_fc_internal_description, job QR).
- External Job Sticker = Layout B, ONE per fp.box (BOX n/N, per-box QR,
  factory company logo, customer-facing notes). Dynamic MASK badge
  (x_fc_masking_enabled) + BAKE block (x_fc_bake_instructions), length-tiered
  notes font. Display logic in fp.job._fp_sticker_data().

Also retains the SO/WO box-sticker MemoryError fix in report_fp_wo_sticker.xml
(per-box loop sourced from fp.receiving.box_count_in + 100-label safety cap).

Verified live on entech: 111 boxes backfilled (31 receivings), External renders
one page per box, Internal one per job, scan endpoint 303->login.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_receiving/controllers/fp_box_controller.py

@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+"""Box scan endpoint. The per-box QR on the External Job Sticker encodes
+``/fp/box/<id>``; scanning it (logged-in operator on the tablet) lands on
+the box's backend form where they can advance its status."""
+from odoo import http
+from odoo.http import request
+
+
+class FpBoxScan(http.Controller):
+
+    @http.route(['/fp/box/<int:box_id>'], type='http', auth='user', website=False)
+    def fp_box_scan(self, box_id, **kw):
+        box = request.env['fp.box'].sudo().browse(box_id).exists()
+        if not box:
+            return request.not_found()
+        # Land on the box form in the web client (operator advances status there).
+        return request.redirect('/web#id=%s&model=fp.box&view_type=form' % box.id)