fix: render select labels before dropdown opens

[reatang]

Description

Follow-up to #211. base-ui's Select.Value falls back to the raw option value when given no children or items mapping, so every SelectValue without children whose option labels differ from their values showed the raw value (e.g. async, Ki, vault-transit) until the dropdown was first opened.

This PR audits all SelectValue usages without children and passes the current label as children (falling back to the placeholder via null when nothing is selected), following the existing pattern in performance-server-list.tsx (sortLabels):

• SSE page — KMS backend select (backendTypeLabels map; the original fix: render KMS backend label in closed select #211 scenario, applied here since that fix was not on this branch's base)
• Bucket info — bucket policy, encryption type, and KMS key selects (KMS key labels come from key tags/description, looked up in kmsKeyOptions)
• Lifecycle new form — both Object Version selects (reuse versionOptions)
• Site replication new/edit forms — TLS verification mode selects and the edit form's Sync state select
• Bucket replication new/edit forms — Mode, TLS verification, and bandwidth unit selects (reuse modeOptions/unitOptions)

Audited and intentionally unchanged because label === value: event ARN select, replication Storage Class selects, lifecycle Storage Type (tier names), and pagination page-size select.

Type notes: BucketPolicyType includes values the policy select does not offer (none, readonly, …) and SiteReplicationSyncState includes unknown, so those two label maps use Partial<Record<…>> with a fallback to the raw value / placeholder.

Type of Change

• Bug fix (non-breaking change which fixes an issue)

Testing

• Unit tests added/updated
• Manual testing completed

pnpm test:run

Ran via corepack pnpm@11.11.0: type-check ✅, lint ✅, format:check ✅ (only the pre-existing components/object/tiff-viewer.tsx failure on main remains), test:run ✅ (401 tests 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

Follow-up to #211.

Additional Notes

The fix pattern relies on base-ui behavior: plain SelectValue children override the raw-value fallback, and null children fall through to the placeholder.