feat: skip quoted replies, signatures and forwarded-message headers by default (configurable with "Also translate quoted text and signatures")
feat: join hard-wrapped plain-text lines before translation
feat: add test button to validate credentials
feat: add translate keyboard shortcut (default: `Ctrl+Shift+X`)
fix: changing the target language retranslates the open message
fix: switching messages while a translation is in flight no longer shows an error or a wrong button label