fix(prisma): colonnes Agent sourceNoteIds / slideTheme / slideStyle + migration

Répare le typecheck Next () : le code utilisait ces champs alors
que le schéma sur main ne les exposait pas encore.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/prisma/schema.prisma

@@ -311,6 +311,9 @@ model Agent {
   isEnabled        Boolean       @default(true)
   targetNotebookId String?
   sourceNotebookId String?
+  sourceNoteIds    String?
+  slideTheme       String?
+  slideStyle       String?
   tools            String?       @default("[]")
   maxSteps         Int           @default(10)
   notifyEmail      Boolean       @default(false)