Update Databento to support v3 and report pipeline failures

[gabbypolito]

Airflow logs showed DBN v3 responses failing to decode with the older Databento packages. The pipeline also swallowed symbol-processing errors and reported success even when these errors occurred.

Changes:

• Pin databento to 0.83.0 and databento-dbn to 0.65.0; regenerate the nested project's Poetry lockfile.
• Update Docker's Poetry version to 2.3.3.
• Let all symbols finish, then fail the task if any symbol raised an error.
• Add a synthetic DBN v3 fixture, decoder test, and failure-reporting regression tests.

Validation:

• Old decoder reproduced the logged DBN version error.
• Updated decoder passed the synthetic test, including in the Linux amd64 Airflow image.
• Five failure-reporting regression tests passed.

Production containers and server code remain unchanged. A real Databento fetch, database insertion, and historical backfill still need verification after deployment.

[gabbypolito]

I didn't commit all my changes.