feat(api): add V2 JSON:API relationship endpoint for GameHash resources

[wescopeland]

This PR adds a V2 API relationship endpoint for GameHash resources, accessible via GET /games/{game}/hashes. This provides the functionality of V1's API_GetGameHashes endpoint. Things worth noting:

• Hashes are accessed exclusively via the relationship route. There is (currently) no standalone index, but one may be desirable later.
• The labels attribute is parsed from its stored comma-separated string into a JSON array.
• All compatibility states are returned by default. The filter[compatibility] param supports comma-separated values to filter by one or more states (eg: compatible, incompatible, untested, patch-required).
• Soft-deleted hashes are automatically excluded.
• The game relationship can be included via ?include=game.

How to test this PR

# Get paginated hashes for a game (50 per page)
curl --request GET \
  --url http://localhost:64000/api/v2/games/1/hashes \
  --header 'X-API-Key: {redacted}'

# Get only compatible hashes (matches V1 API behavior)
curl --request GET \
  --url 'http://localhost:64000/api/v2/games/1/hashes?filter[compatibility]=compatible' \
  --header 'X-API-Key: {redacted}'

# Get compatible and incompatible hashes
curl --request GET \
  --url 'http://localhost:64000/api/v2/games/1/hashes?filter[compatibility]=compatible,incompatible' \
  --header 'X-API-Key: {redacted}'

# Get hashes with game data included
curl --request GET \
  --url 'http://localhost:64000/api/v2/games/1/hashes?include=game' \
  --header 'X-API-Key: {redacted}'

# Custom pagination (page 2, 25 per page)
curl --request GET \
  --url 'http://localhost:64000/api/v2/games/1/hashes?page[number]=2&page[size]=25' \
  --header 'X-API-Key: {redacted}'