chore: upgrade i18next 26, prettier 3, fontsource-variable, domhandler 6, lint-staged 17

- i18next 23->26 + react-i18next 15->17
- prettier 2->3, reformat all files
- replace @fontsource/inter with @fontsource-variable/inter 5, update import path
- domhandler 5->6 (aligns with transitive deps)
- lint-staged 16->17

src/ext.d.ts

@@ -25,7 +25,7 @@ declare module 'browser-encrypt-attachment' {
 
   export function decryptAttachment(
     dataBuffer: ArrayBuffer,
-    info: EncryptedAttachmentInfo
+    info: EncryptedAttachmentInfo,
   ): Promise<ArrayBuffer>;
 }