fix: handle readonly bucket states safely

[cxymds]

Pull Request

Description

Fix readonly bucket browsing so permission-limited S3 responses are represented accurately instead of redirecting users or inventing trusted state.

• Keep users on the bucket page when HeadBucket returns 403; only redirect for a definitive missing bucket response.
• Show unknown access policy as - when GetBucketPolicyStatus cannot be read instead of incorrectly labeling the bucket private.
• Keep GetBucketVersioning fail-closed for deletion safety without showing the generic Failed to get data banner.
• Distinguish object-list 403 and load failures from a confirmed empty bucket.
• Add an announced DataTable error state and preserve the upstream filtered-empty behavior.

The root cause was that independent permission failures were being collapsed into unrelated states: 403 from HeadBucket triggered navigation, policy-status failure became false, and object-list failure became an empty result.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated
• Manual testing completed

pnpm install --frozen-lockfile
pnpm tsc --noEmit
pnpm lint
pnpm test:run
pnpm prettier --check <changed files>
git diff --check

373 tests pass. TypeScript, ESLint, changed-file Prettier, lockfile sync, and diff checks pass.

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass
• No new dependencies added, or they are justified

Related Issues

None.

Screenshots (if applicable)

Not included; the error states require permission-specific S3 responses.

Additional Notes

The full-repository pnpm prettier --check . currently reports a pre-existing formatting issue in app/(dashboard)/sse/page.tsx. That file is not changed by this PR; all files changed here pass Prettier.