fix: subcontractor PDF quality, footer on all pages, header gap

- Canvas 3x scale + JPEG 0.97 (matches main invoice quality)
- Footer drawn on every page canvas
- Continuation header gap increased (headerH+28 → +50 with label)
- Pagination pre-calculated before rendering (no mid-render addPage)
- 'PO Date' label → 'Invoice Date'

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

.claude/settings.local.json

@@ -19,7 +19,8 @@
       "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 *)",
       "Bash(git commit -q -m 'style: card-bg dark-based alpha to match Safari panel look *)",
-      "Bash(git commit -q -m 'style: white-based card-bg 0.07, blur 12px→20px for less transparency *)"
+      "Bash(git commit -q -m 'style: white-based card-bg 0.07, blur 12px→20px for less transparency *)",
+      "Bash(git commit -q -m 'fix: subcontractor PDF quality, footer on all pages, header gap *)"
     ]
   }
 }