feat(mapbox): upgrade Mapbox provider to Geocoding API v6 (2.0.0)

[davidbarratt]

Summary

• Upgrades Geocoder\Provider\Mapbox\Mapbox in place to the Mapbox Geocoding API v6 (/search/geocode/v6/forward and /search/geocode/v6/reverse), as a major version (2.0.0) of geocoder-php/mapbox-provider
• Adds v6 Structured Input (typed address fields via query data), autocomplete / proximity / worldview query data, a new 4th constructor argument bool $permanent, TYPE_STREET / TYPE_BLOCK / TYPE_SECONDARY_ADDRESS constants, and MapboxAddress::getMatchCode() / getMatchConfidence() / getAccuracy()
• Removes the v5 endpoints, GEOCODING_MODE_*, TYPE_POI* and fuzzy_match; every breaking change is listed in the provider CHANGELOG 2.0.0 (v5 users: pin to geocoder-php/mapbox-provider:^1.5)

Closes #1237

Test Plan

• composer test — full suite green (1049 tests); Mapbox: 45 tests incl. 7 v6 integration fixtures + 4 provider-integration fixtures replayed from .cached_responses with the placeholder key (CI-safe)
• composer analyse — PHPStan level 6 clean
• composer cs — clean on all touched files
• TDD throughout: the failing-tests commit (test(mapbox): add failing tests for the v6 API) is followed by the implementation commits that turn the suite green
• Fixtures recorded against the live v6 API (2026-08-28); all v5 fixtures removed

[davidbarratt]

@jbelien I've run the cs:fix script locally and committed the output, could you run the CI again? Did you have any other comments or feedback? Thanks!