* add k3s update center
* fix update center status timeouts
* Polish update center settings UI
* Document k3s update center
* Refocus update center docs for users
* Clarify k3s migration path in docs
- Implemented `normalizeMigrationInput` to standardize database migration input for sqlite, mysql, and postgres.
- Added `maskConnectionString` to obscure sensitive credentials in connection strings.
- Created comprehensive tests for migration input normalization and connection string masking.
- Established database schema creation logic for multiple dialects (sqlite, mysql, postgres).
- Developed functions for managing database transactions, including begin, commit, and rollback.
- Implemented data insertion logic from backup snapshots into the target database.
Cita