nationex: normalize additional tracking statuses

[HansDaigle]

Summary

• expand Nationex tracking status normalization for additional carrier states
• map Creation and DataReceived to pending
• map partial delivery, pickup, cancellation, return, and pickup-ready statuses explicitly
• fallback unknown carrier states to unknown
• keep POD/base64 image handling out of scope for this PR

Review updates

• Rebuilt on current karrioapi/community:main as a single focused commit.
• Confirmed current community main already has the Nationex rate Content-Type: application/json fix, so this PR now carries only tracking status normalization.

Validation

.venv/bin/python -m pytest plugins/nationex/tests/nationex -q

Result: 14 passed, 1 warning, 19 subtests passed.

[HansDaigle]

Recommendation for tracking normalization work: prefer when querying carrier tracking APIs (including via Karrio). We verified localized descriptions (e.g., FR) can vary in wording, while the normalized status remains stable; using English reduces parser drift and keeps mappings deterministic across carriers.

[HansDaigle]

Tracking note/TODO: Nationex POD images are returned as base64 payloads (not URL refs). We intentionally removed image-fetching for now to avoid persisting large blobs in tracking payload/storage. Follow-up: decode base64, upload to object storage (S3/R2/etc), and persist only generated URLs.

[HansDaigle]

Rebased against current karrioapi/community:main. Current community main already has the rate Content-Type fix, so this PR is now limited to Nationex tracking status normalization. Local verification: .venv/bin/python -m pytest plugins/nationex/tests/nationex -q -> 14 passed, 1 warning, 19 subtests passed.