fix(uph): persistent party filtering and HTML fix in duplicate warning

[Sendipad]

Description

This PR now includes:

1. Persistent Party Field Filtering
   • Updated uph.party.set_party_query to fetch party_master dynamically and re-apply on field focus. This keeps filtering active even if other scripts override it or the field is cleared.
   • Moved query initialization to onload and refresh in utils.js for better reliability on draft/existing documents.
2. HTML Formatting Fix
   • Fixed broken <li> tags in the duplicate document warning message (party.js).
3. Voucher Sync Reliability + Scale Tests
   • Linking/creating Party Master now attempts a synchronous voucher update first, with a safe fallback to enqueue.
   • Added unit coverage for scale cases (100 Journal Entries + 10 Payment Entries) to verify party_master backfill on link.

Verification

• Not run locally in CI (see notes below).

Notes

• Tests added: test_link_customer_updates_large_volume_vouchers in uph/tests/test_unlinked_resolver.py.