fix(types): drop .ts extensions + narrow Uint8Array buffer type

- shared-types/index.ts: drop .ts import extensions (web-app tsconfig
  has no allowImportingTsExtensions; bundler resolution handles it)
- backup/format.test.ts: narrow buildZip return to Uint8Array<ArrayBuffer>
  so the Blob() constructor accepts it under strict lib.dom

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-types/src/index.ts

@@ -5,25 +5,25 @@
  */
 
 // Theme types
-export * from './theme.ts';
+export * from './theme';
 
 // Auth types
-export * from './auth.ts';
+export * from './auth';
 
 // UI types
-export * from './ui.ts';
+export * from './ui';
 
 // Common utility types
-export * from './common.ts';
+export * from './common';
 
 // Contact types for cross-app integration
-export * from './contact.ts';
+export * from './contact';
 
 // Landing page configuration types
-export * from './landing-config.ts';
+export * from './landing-config';
 
 // AI structured-output Zod schemas (shared between mana-api + web frontend)
-export * from './ai-schemas.ts';
+export * from './ai-schemas';
 
 // API types
 export interface User {