Tokens previously lasted 30 days with no revocation path. Expiry is now
24 hours and every token carries a unique jti (UUID hex) to support future
revocation checks.
Expand blocked keywords to cover parquet_scan, read_csv_auto, query_table,
iceberg_scan, delta_scan, call, URL schemes (http/https/s3/gcs), and
additional file-scan functions. Set enable_external_access=false on the
non-read-only analytics connection path. Add three new tests covering
parquet_scan, read_csv_auto, and query_table blocking.
Prevents production deployments from silently using a hardcoded default
secret. TESTING=1 still resolves to a built-in test key so the existing
test suite is unaffected. Adds a test that verifies the RuntimeError is
raised when neither JWT_SECRET_KEY nor TESTING is set.