fix(s3): use raw multipart upload pagination markers - #1487

What kind of change does this PR introduce?

Bug fix. Fixes #1486.

What is the current behavior?

ListMultipartUploads rejects valid object-key/upload-ID markers with Invalid Parameter continuation token, because it expects private base64 tokens. Truncated responses also wrap both next markers in those tokens, contrary to S3's marker contract.

What is the new behavior?

Pass raw keys and upload IDs to the existing database pagination path. Return the last listed key/upload ID as next markers, URL-encoding key response fields when EncodingType: 'url' is requested. Remove the two now-unused multipart-only token helpers.

Regression coverage exercises raw marker input, a two-page same-key listing, URL-encoded keys containing Unicode/colon/slash/space, echoed markers, and the final untruncated page. The existing colon-preservation test now uses an S3 key marker directly.

Additional context

Validation on upstream bc38cb97:

• Existing handler/database baseline: 121 tests passed.
• All three new regression cases fail with the unchanged upstream handler; all three pass with the fix.
• Focused handler/database/router tests: 279 passed (npm run test:unit -- --maxWorkers=2 src/storage/protocols/s3/s3-handler.test.ts src/storage/database/pg.test.ts src/http/routes/s3/router.test.ts).
• Full unit suite: 2,782 tests / 166 files passed (npm run test:unit -- --maxWorkers=2).
• npm run build, npm run lint (Biome and Prettier), and git diff --check passed.
• Docker integration tests were not run: the isolated Compose stack could not bind port 9000, which was already allocated. Only this task's Compose resources were removed. An initial unbounded unit run was interrupted after unrelated pool-test timeouts under resource contention; the bounded full run passed.

Compatibility: previously saved private base64 multipart markers must be discarded and listings restarted. Markers now follow the S3 API contract; object-list continuation tokens are unaffected. No database or dependency changes.

Related merged #1346 addresses multipart ordering and #1384 addresses response shape; this fixes the distinct wire-marker format. Searches of issues/PRs/comments, discussions, commits, and local history found no blocking overlap.