Workflow metadata endpoints accept a missing workflow ID

### Feature Summary

The workflow name and description endpoints pass a missing `wid` query parameter into the database predicate. The empty result becomes a 204 response, so an invalid request is indistinguishable from a successful response with no content.

Before: missing `wid` returns 204.

Expected: missing `wid` returns 400, while valid workflow metadata requests keep returning 200.

Reproduction evidence:

1. Launch Texera from current `main`.
2. Request `GET /api/workflow/workflow_name` without `wid` and observe 204.
3. Request `GET /api/workflow/workflow_description` without `wid` and observe 204.
4. Add a valid `wid` to either request and observe 200.

Version and commit evidence:

1.3.0-incubating-SNAPSHOT (main)

**Commit Hash (Optional)**

98588bf2ab49aac65ebf002496eb057670e6fc07

**What browsers are you seeing the problem on?**

Not browser-specific.

**Relevant log output**

No error is logged because the missing ID is treated as an empty query result.

### Proposed Solution or Design

Expected: missing `wid` returns 400, while valid workflow metadata requests keep returning 200.

### Affected Area

Workflow Engine (Amber)