v1.8.12

CLI/API gaps for 0.6.12

• Expand ~ and allow absolute attachment paths (still reject .. / NUL)
• FilesService.listWebDav for directory listing
• AuthBroker.login({ ephemeral }) omits password from keychain
• logoutAll() for bulk logout
• Clearer --browser error: uses system Chrome/Edge (no Playwright download)
• UA product token Aplanatic-IServ/1.8.12