feat(postcodes/KE): bulk-import 630 Kenya postcodes via Posta Kenya (#1039)

[dr5hn]

Summary

Adds 630 Kenya postcodes from the Posta Kenya office index sourced
from the njoguamos/kenya-postal-codes mirror.

• Coverage: country-only by design.
• Granularity: post-office level — one record per
  (5-digit code, office) pair.

Source & licence

• Source URL: https://raw.githubusercontent.com/njoguamos/kenya-postal-codes/master/src/kenya-postal-codes.json
• Origin: Postal Corporation of Kenya office codes, redistributed by
  njoguamos.
• Each row: "source": "posta-kenya-via-njoguamos"

Validation

• python3 -m py_compile clean.
• 100% of 630 codes match country.postal_code_regex (^(\d{5})$).
• 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 + country FK).
• Idempotent merge verified.
• CI pipeline green.

Refs #1039.

🤖 Generated with Claude Code

[Copilot]

Copilot wasn't able to review any files in this pull request.

[github-actions]

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 630 records. Large contributions require manual review.

Schema Validation (630 records)

✅ All records passed validation

Cross-Reference Validation

✅ 630 reference(s) verified

Source URL Verification

✅ 2 source URL(s) accessible

---

✅ All checks passed | Status: Ready for review