Add integration test for price alert endpoint triggering when threshold is crossed

[Chucks1093]

Summary

The price alert endpoint should trigger a notification when a creator's price crosses the user-defined threshold. An integration test should set an alert, update the price snapshot to cross the threshold, and confirm the alert delivery was attempted.

Scope

• Create a price alert for a creator at threshold 500
• Update the price snapshot from 400 to 600 (crossing the threshold)
• Assert the alert delivery job was enqueued
• Assert the alert is marked as triggered and not re-queued on the next snapshot update

Acceptance Criteria

• Delivery job enqueued when price crosses threshold
• Alert marked triggered after first crossing
• Alert not re-triggered on subsequent snapshot updates above threshold
• Alert not triggered when price moves but does not cross the threshold

ETA: 12 hours

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