fix(files): prevent autosave data loss on load lag and binary files

Guard FilesView autosave until the selected file has finished loading,
refuse binary/PDF/office/archive text saves, and add a persisted global
autoSaveEnabled setting (default true) under Settings → General.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/lib/api/types.ts

@@ -637,6 +637,7 @@ export interface SettingsPayload {
   nativeNotificationsEnabled?: boolean;
   notificationMode?: 'always' | 'hidden-only';
   autoDeleteEnabled?: boolean;
+  autoSaveEnabled?: boolean;
   autoDeleteAfterDays?: number;
   sessionRetentionAction?: 'archive' | 'delete';
   followUpBehavior?: 'steer' | 'queue';