feat(postcodes/UA): bulk-import 15,086 Ukraine postcodes via Ukrposhta (#1039)

[dr5hn]

Summary

Adds 15,086 Ukraine postcodes covering every city/town in the Ukrposhta
catalogue, sourced from the rvolykh/UAPostcodes SQL dump.

• Coverage: 100% region resolution (27/27 in states.json), spanning
  all 24 oblasts plus the Autonomous Republic of Crimea and the two
  cities of national importance (Kyiv, Sevastopol).
• Format: 5-digit Ukrposhta codes; locality_name in Ukrainian
  Cyrillic.

How it works

The source ships three SQL dumps. The importer parses
cities.sql (City rows have district_id not region_id) and
joins to districts.sql to obtain the oblast id, then maps that to
CSC's states.json iso2 via a hand-curated 27-entry table.

Source & licence

• Source URL (cities): https://raw.githubusercontent.com/rvolykh/UAPostcodes/master/db_scripts/cities.sql
• Source URL (districts): https://raw.githubusercontent.com/rvolykh/UAPostcodes/master/db_scripts/districts.sql
• Origin: Ukrposhta publicly published index, redistributed by rvolykh.
• Each row: "source": "ukrposhta-via-rvolykh"

Validation

• python3 -m py_compile clean.
• 100% of 15,086 codes match country.postal_code_regex (^(\d{5})$).
• 100% of records resolve a valid state_id whose country_id == 230
  and whose iso2 matches state_code.
• No auto-managed fields (id, created_at, updated_at, flag).

Test plan

• Importer compiles and runs on a clean checkout.
• Cross-reference validator passes (regex + FK + state_code agreement).
• Idempotent merge verified.
• CI pipeline green.

Refs #1039.

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CSC Validation Report

PR Format

• ✅ Description provided
• ✅ Data source linked
• ✅ Issue linked (recommended for data changes)
• ✅ Justification / context provided

Labels applied: data:postcodes, large-contribution

⚠️ Large Contribution

This PR contains 15086 records. Large contributions require manual review.

Schema Validation (15086 records)

✅ All records passed validation

Cross-Reference Validation

✅ 30172 reference(s) verified

Source URL Verification

✅ 3 source URL(s) accessible

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✅ All checks passed | Status: Ready for review