feat(updates): add container release mode support

[chbndrhnns]

Summary

Extends OpenShip's release drift and deployment engines to support container image release tracking for projects that consume prebuilt Docker images from upstream GitHub releases (e.g. ghcr.io/org/repo:tag).

Fixes #694

Details

• ReleaseSource & Image Templating:
  • Added optional imageTemplate to ReleaseSource interface and schema.
  • Added renderImageTemplate(template, { version, tag? }) in @repo/core to substitute {version} / {tag} placeholders, or update the image tag portion when no placeholders are present.
• Drift Evaluation (apps/api):
  • Enabled "release" drift mode when isReleaseProvider(p.gitProvider) || Boolean(p.releaseSource).
  • Added cache key tracking for imageTemplate so template updates invalidate cached drift.
  • Added fallback version resolution from deployed image tags or branches when deployment.releaseVersion is unset.
• Build & Deploy Pipeline (apps/api):
  • In applyReleaseSourceToSnapshot, detects container release mode (source.imageTemplate, snapshot.buildImage without tarball templates, sourceKind === "image", or buildKind === "prebuilt"), renders the target image ref, sets snapshot.buildImage and snapshot.releaseVersion, and skips tarball dist downloads.
  • In preflight.ts, allows container release deployments to pass without requiring a repository URL or local directory.
• Testing:
  • Unit tests for image template rendering and placeholder validation in packages/core/test/project-source.test.ts.
  • Unit tests for release drift evaluation in apps/api/test/modules/updates/drift-evaluation.test.ts.
  • Unit tests for container release snapshot resolution in apps/api/test/modules/deployments/container-release-deploy.test.ts.