Companion to the bot-side change: the variables hint now renders two
groups — type-specific vars and common ones ({service_name},
{cabinet_url}, {support_username}, {username}, {email}, {date}) that
work in every template. The block is visible even for types with no
vars of their own (previously it was hidden entirely, looking like
placeholders didn't exist). Common chips insert at cursor the same way.
Companion to the bot-side fix: defaults now arrive with {placeholders}
instead of baked-in sample values (example.com links).
- inline preview tab (iframe srcDoc) — works on mobile and in Telegram;
the separate desktop-only preview page and its route are removed
- preview/test render the CURRENT editor content with sample values
- test email: recipient input + detailed backend error messages
- variable chips insert at cursor instead of copying to clipboard
- 'insert default template' button to migrate broken saved overrides
- fa added to language tabs
