Configurable self-hosted artifact retention

Self-hosted Tuist instances can now automatically clean up artifact files from object storage. Operators can set independent retention windows for cache artifacts, app previews, build archives, run artifacts, test attachments, and shard bundles.

Configure the windows through the Helm chart:

server:
  artifactRetentionDays:
    cacheArtifacts: 30
    appPreviews: 30
    buildArchives: 60
    runArtifacts: 30
    testAttachments: 30
    shardBundles: 14

Each artifact family also has its own environment variable for deployments that do not use Helm. Leaving a family unset or blank keeps its cleanup disabled. Cleanup removes artifact files only and preserves the associated PostgreSQL and ClickHouse metadata used by dashboards and analytics.