fix(party): Transaction Health incorrect false positives on amended docs

[Sendipad]

The code formerly checked the `amended_from` field on the canceled document itself, which is always empty. This fix refactors the logic to check if another document has an `amended_from` pointing to the canceled document's name, accurately aligning with standard Frappe tracking behavior.

Changes:

• Refactored scan queries for both standard and child doctypes in `run_transaction_policy_scan`
• Updated resolving logic inside `sync_transaction_health_issues`
• Fixed tally in `get_health_counts`
• Created robust unit test coverage in `test_transaction_health.py`"