## Description
Sessions created by logins from the Chatwoot Mobile app currently render
as "Unknown Device" in the dashboard sessions UI. The mobile app's HTTP
layer sends:
- Android: `User-Agent: okhttp/4.9.2`
- iOS: `User-Agent: Chatwoot/<build> CFNetwork/<v> Darwin/<v>`
Neither pattern is classifiable by the `browser` gem, so
\`browser_name\`, \`platform_name\`, and \`device_name\` all end up
"Unknown".
This change adds a backend-only fallback in
\`UserSessionTrackingService\`. When \`Browser.new(ua)\` returns
"Unknown Browser" and the UA matches a known Chatwoot Mobile pattern,
the labels are overridden to \`Chatwoot Mobile\` + \`Android\` /
\`iPhone\`. The Vue sessions list (\`ActiveSessions.vue\`) then renders
"Chatwoot Mobile on Android" or "Chatwoot Mobile on iPhone" with the
smartphone icon.
This is the immediate floor. A follow-up will add structured
\`X-Chatwoot-*\` headers from the mobile app so we can render full
version + device model.
Fixes INF-75.
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
- Added specs
## Checklist:
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules
