Insomnia Import

> ℹ️ _This issue was partially AI-generated and may contain technical inaccuracies._

**Is your feature request related to a problem? Please describe.**
Teams migrating from Insomnia have no import path into Trufos.

**Describe the solution you'd like**
Support importing Insomnia collections (export format v4 JSON/YAML), mapping requests, folders, environments, and auth into Trufos collections.

**Describe alternatives you've considered**
Asking users to migrate via Postman format as an intermediate step.

**Additional context**
Complements existing Postman import (#750, #751) and the planned Bruno import (#196). Should reuse the import service in `src/main/import/`.

Start in src/main/import/ and review the existing Postman import work referenced by #750 and #751. Determine how Insomnia export format v4 JSON/YAML represents requests, folders, environments, and auth, then verify that each maps into Trufos collections. Done means users can import those elements without using Postman as an intermediate step.

Written by the indexing model from the issue text.