fix: recursive dict in labels during schedule discovery in LabelScheduleSource

[danfimov]

Fixed issues:

• When labels are passed inside schedule, the ScheduledTask.labels field contained a recursive structure - discussion;
• When a user provided schedule_id inside schedule, it was always replaced with a random UUID.

Also deleted duplicated tests: tests/schedule_sources/test_label_based.py are literally the same as in tests/scheduler/test_label_based_sched.py.

[Copilot]

Pull Request Overview

This PR fixes two issues in the LabelScheduleSource class related to schedule discovery: preventing recursive dictionary structures in task labels when labels are passed within schedules, and preserving user-provided schedule_id values instead of always overwriting them with random UUIDs. The fix involves deep copying task labels and excluding the schedule key to avoid recursion, and respecting user-provided schedule IDs.

Key changes:

• Modified label handling in LabelScheduleSource.startup() to deep copy task labels and remove the schedule key before merging
• Updated schedule ID generation to use user-provided schedule_id when available
• Removed duplicate test file and enhanced existing tests with new test cases

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
taskiq/schedule_sources/label_based.py	Fixed recursive label structure by deep copying and filtering task labels, and preserved user-provided schedule IDs
tests/scheduler/test_label_based_sched.py	Added test cases for labels inside schedules and custom schedule IDs, plus verification that original task labels remain unchanged
tests/schedule_sources/test_label_based.py	Deleted duplicate test file

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