feat(perms): drop dead document export permissions; seed the 12 survivors via migration

offers.export/orders.export/invoices.export gated nothing on the backend (PDF
routes enforce *.view); they only toggled frontend buttons and showed dead
role checkboxes. Migration deletes them (+ role grants) and idempotently seeds
the 12 enforced doc perms (offers/orders/invoices x view/create/edit/delete) +
admin grant, so a fresh prod DB has them (closes the seed-only drift gap).
Route reverts to orders.view; the 8 frontend *.export checks now use *.view.

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

src/admin/pages/OfferDetail.tsx

@@ -1081,7 +1081,7 @@ export default function OfferDetail() {
             </Box>
           </Box>
           <Box sx={headerActionsSx}>
-            {isEdit && hasPermission("offers.export") && (
+            {isEdit && hasPermission("offers.view") && (
               <Button
                 onClick={handlePdf}
                 variant="outlined"