fix(reports): use table layout for BoL signature row, drop flex on sig-box

Last fix added page-break-inside: avoid but the boxes still split
because wkhtmltopdf 0.12 ignores that rule inside flex containers,
and BOTH the .sig-box (display: flex) AND the Bootstrap .row
wrapper were flex.

Replace both with non-flex equivalents:

- .sig-box: dropped `display: flex` + `flex-direction: column` +
  `justify-content: flex-end`. Layout now uses padding + a fixed-
  height .sig-line block + the muted label below. Same visual
  result, but a plain block element so wkhtmltopdf honors the
  page-break rule.

- Replaced `<div class="row">` + 3 `<div class="col-4">` (Bootstrap
  flex grid) with a `<table class="sig-table">` containing one row
  of three 33% tds. wkhtmltopdf treats table rows as atomic for
  page-breaking, so the whole signature row now stays on a single
  page.

Verified with pypdf: page 1 has the cert statement, page 2 has
all three signature labels together — no more sliced boxes.

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

fusion_plating/fusion_plating_reports/__manifest__.py

@@ -3,7 +3,7 @@
 # License OPL-1 (Odoo Proprietary License v1.0)
 {
     'name': 'Fusion Plating — Reports',
-    'version': '19.0.4.3.0',
+    'version': '19.0.4.4.0',
     'category': 'Manufacturing/Plating',
     'summary': 'PDF reports for Fusion Plating: quote, SO, WO, packing, BoL, CoC, invoice, receipt, quality + compliance.',
     'depends': [