fix: subcontractor PDF title + multi-page support

- 'PURCHASE ORDER' → 'SUBCONTRACTOR INVOICE'
- Items loop now calls addPage() when hitting safeBottom (792-80pt)
- Continuation pages get header with invoice number + '(continued)'
- Summary/Notes sections also page-break if needed
- Footer text updated to match invoice context
- Footer line position dynamic (tracks y), not hardcoded at 704

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.local.json

@@ -16,7 +16,8 @@
       "Bash(sed -n '1,15p' src/pages/external/ExternalMyInvoices.jsx)",
       "Bash(sed -n '1,15p' src/pages/client/ClientMyInvoices.jsx)",
       "Bash(git commit -q -m 'fix: restore popupOverlayStyle import in ExternalMyInvoices *)",
-      "Bash(git commit -q -m 'style: increase card-bg alpha to match Safari rendering *)"
+      "Bash(git commit -q -m 'style: increase card-bg alpha to match Safari rendering *)",
+      "Bash(git commit -q -m 'fix: subcontractor PDF title + multi-page support *)"
     ]
   }
 }