Add Sentry integration for Gust and DAG run failures

[marciok]

Summary

Add an optional Sentry integration so Gust operators can monitor application exceptions and failed DAG/task executions from their existing observability workflow.

The integration should attach enough Gust context to diagnose a failure while preventing secrets and sensitive task data from being reported.

Proposed scope

• Capture unhandled exceptions from Gust runtime processes.
• Report failed DAG and task executions with structured context.
• Include safe identifiers and metadata such as:
  • DAG name;
  • run ID;
  • task name and mapped task index;
  • run and task status;
  • retry attempt;
  • Gust version and environment.
• Link Sentry events back to the corresponding Gust run dashboard when a dashboard base URL is configured.
• Record or expose the Sentry event ID from the Gust run/task view when practical.

Configuration

• The integration is disabled by default.
• Support configuration through standard application configuration and environment variables.
• Allow operators to configure DSN, environment, release, sample rate, and enabled event types.
• Provide hooks or configuration for filtering and redacting event data.
• Do not require Sentry for Gust to start or execute DAGs.

Safety and resilience

• Never send secrets, credentials, complete task payloads, or task results by default.
• Apply redaction before an event leaves the Gust process.
• Sentry outages or reporting failures must not change DAG execution status or crash Gust processes.
• Avoid duplicate events for the same failure and retry attempt.
• Make network reporting asynchronous and bounded.

Acceptance criteria

• Operators can enable Sentry through documented configuration.
• An unhandled Gust exception produces a Sentry event with useful Gust metadata.
• A failed DAG task produces a Sentry event with the correct DAG, run, task, mapped index, and retry context.
• Events can link to the relevant Gust run dashboard.
• Sensitive fields are excluded or redacted by default.
• Gust continues operating normally when Sentry is unavailable or misconfigured.
• Add focused tests for configuration, event metadata, redaction, deduplication, and reporting failures.
• Document setup and provide an example configuration.