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>

prisma/seed.ts

@@ -95,12 +95,6 @@ const PERMISSIONS: {
     module: "offers",
     description: "Mazat nabídky",
   },
-  {
-    name: "offers.export",
-    display_name: "Exportovat nabídku",
-    module: "offers",
-    description: "Exportovat nabídky do PDF",
-  },
 
   // Objednávky
   {
@@ -127,12 +121,6 @@ const PERMISSIONS: {
     module: "orders",
     description: "Mazat objednávky",
   },
-  {
-    name: "orders.export",
-    display_name: "Exportovat objednávku",
-    module: "orders",
-    description: "Exportovat objednávky do PDF",
-  },
 
   // Faktury
   {
@@ -159,12 +147,6 @@ const PERMISSIONS: {
     module: "invoices",
     description: "Mazat faktury",
   },
-  {
-    name: "invoices.export",
-    display_name: "Exportovat fakturu",
-    module: "invoices",
-    description: "Exportovat faktury do PDF",
-  },
 
   // Projekty
   {