FastAPI uses __pydantic_validator__.validate_python() which bypasses
model_validate() overrides. Switch to @model_validator(mode='after')
which the Pydantic Rust core always calls, so jira_token_set is now
correctly derived from the excluded jira_api_token field.
Also add a 10s timeout to the jira-test endpoint and better error
messages (the Atlassian library's "Expecting value" JSON error was
ambiguous).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>