Implement 'Add Password' and 'Change Permissions' tools in V2 (#4195)

# Description of Changes
Implement Add Password and Change Permissions tools in V2 (both in one
because Change Permissions is a fake endpoint which just calls Add
Password behind the scenes).

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Co-authored-by: James <[email protected]>

frontend/src/types/fileContext.ts

@@ -5,7 +5,18 @@
 import { ProcessedFile } from './processing';
 import { PDFDocument, PDFPage, PageOperation } from './pageEditor';
 
-export type ModeType = 'viewer' | 'pageEditor' | 'fileEditor' | 'merge' | 'split' | 'compress' | 'ocr' | 'convert' | 'sanitize';
+export type ModeType = 
+  | 'viewer' 
+  | 'pageEditor' 
+  | 'fileEditor' 
+  | 'merge' 
+  | 'split' 
+  | 'compress' 
+  | 'ocr' 
+  | 'convert' 
+  | 'sanitize'
+  | 'addPassword'
+  | 'changePermissions';
 
 export type ViewType = 'viewer' | 'pageEditor' | 'fileEditor';