* 🐛 Fix several issues in RPC command handlers
- Reject circular library references in link-file-to-library
- Add explicit team permission check in search-files
- Constrain search-term max length to 250 chars
- Include :deleted-at in file ETag for COND caching
- Move storage I/O outside DB transaction in create-file-thumbnail
AI-assisted-by: deepseek-v4-pro
* 📎 Check perms before circular link checks
* 🐛 Handle circular library reference error
Catch :circular-library-reference error from backend when linking
files to libraries. Show user-friendly toast notification instead of
propagating unhandled error. Add English and Spanish translations.
AI-assisted-by: qwen3.7-plus
6c2b61e1ad