feat: add ModelCharacteristics view and fix BFCL converter data quality

fix (expression-builder): reject empty expressions and fix null vs undefined invalid state

feat: schema v2, tool_calling evaluation, BFCL converter, UI polish, and expression fixes (#18)

chore (maintainance): Update depdencies, copyright and minimal support for chat template.

feat (expression): Experimental support for expression based filtering in model behavior. (#13)