Portal: add nullable System Name to LicenseKey with per-account unique index

Adds systemName (as typed, trimmed) and systemNameLower (case-folded) to
LicenseKey plus a unique index on (userId, systemNameLower) so names are
case-insensitively unique per account when non-null. Additive and
reversible; migration tested up/down. Regenerates the Prisma client.

src/lib/generated/prisma/internal/prismaNamespace.ts

@@ -2020,7 +2020,9 @@ export const LicenseKeyScalarFieldEnum = {
   createdAt: 'createdAt',
   lastValidatedAt: 'lastValidatedAt',
   userId: 'userId',
-  email: 'email'
+  email: 'email',
+  systemName: 'systemName',
+  systemNameLower: 'systemNameLower'
 } as const
 
 export type LicenseKeyScalarFieldEnum = (typeof LicenseKeyScalarFieldEnum)[keyof typeof LicenseKeyScalarFieldEnum]