Drop Duplicate Exclusion doctype and remove Party workspace references

[Sendipad]

Motivation

• The Duplicate Exclusion doctype is deprecated and should be removed from the codebase to avoid exposing a stale UI surface and duplicated functionality.
• Clean up the Party workspace so users no longer see links/shortcuts to the removed doctype and the workspace JSON remains consistent with repository serialization style.

Description

• Deleted the doctype implementation files under uph/party/doctype/duplicate_exclusion/ including duplicate_exclusion.json, duplicate_exclusion.py, duplicate_exclusion.js, test_duplicate_exclusion.py, and __init__.py.
• Removed all Duplicate Exclusion entries from the Party workspace uph/party/workspace/party/party.json shortcuts and links and restored the content serialization format to the repository style.
• Left historical migration patch references (e.g. uph.patches.migrate_duplicate_exclusion_to_party_issue) and localization strings unchanged to preserve migration history and avoid altering patches that are defensive when the doctype is absent.

Testing

• Ran python -m py_compile uph/party/page/data_quality_dashboard/data_quality_dashboard.py and it completed successfully.
• Validated workspace JSON with python -m json.tool uph/party/workspace/party/party.json >/dev/null and this validation succeeded.
• Captured a browser screenshot of the Party workspace after the change (artifact path shown in commit metadata) as an automated visual check.

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Codex Task