feat(celery): allow custom monitor config for beat tasks - #7839

Description

Celery Beat auto-instrumentation (CeleryIntegration(monitor_beat_tasks=True)) derives the cron monitor config from the schedule only (schedule + timezone), so there is no way to set max_runtime, checkin_margin, failure_issue_threshold, recovery_threshold, or owner on the monitors the SDK creates.

Consequence: a task that can legitimately run longer than Sentry's default 30-minute max_runtime is reported as a timed-out cron failure even though it completes successfully. The only workaround is to exclude it from auto-instrumentation and re-declare the schedule in a manual @sentry_sdk.monitor(..., monitor_config=...) call, which is awkward when the schedule differs per environment.

This adds a beat_task_monitor_config option to CeleryIntegration: a mapping of Celery Beat task name to a partial MonitorConfig that is merged over the config derived from the schedule.

import sentry_sdk
from sentry_sdk.integrations.celery import CeleryIntegration

sentry_sdk.init(
    integrations=[
        CeleryIntegration(
            monitor_beat_tasks=True,
            beat_task_monitor_config={
                "nightly-cleanup": {"max_runtime": 120, "checkin_margin": 10},
            },
        ),
    ],
)

The SDK still derives schedule and timezone; the override only needs the extra fields, and can still override the derived values if explicitly provided.

Changes:

• CeleryIntegration: new beat_task_monitor_config option.
• _get_monitor_config: accepts and merges monitor config overrides.
• _apply_crons_data_to_schedule_entry: looks up the override for the schedule entry and passes it through (covers both the default scheduler and RedBeat, which share this path).
• Tests: merge into the derived config, schedule override, and per-task matching (unmatched tasks are unaffected).

Issues

• resolves: Celery Beat auto-instrumentation: allow configuring monitor limits (max_runtime, checkin_margin, ...) #7838

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community