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/Offers.tsx

@@ -695,7 +695,7 @@ export default function Offers() {
                 </IconButton>
               )
             )}
-            {hasPermission("offers.export") && (
+            {hasPermission("offers.view") && (
               <IconButton
                 size="small"
                 onClick={() => handlePdf(q)}