test: reach 80% coverage threshold in services/admin

[ascariandrea]

Current state

Currently 0% — only one spec file exists (`useStreamingChat.spec.ts`) and the coverage `include` glob does not match it. Thresholds are set to 0% as a placeholder.

Metric	Actual	Target
Statements	~0%	80%
Branches	~0%	80%
Functions	~0%	80%
Lines	~0%	80%

Context

A spec project was added in #3334 (`services/admin/vitest.config.spec.ts`) to pick up unit tests. The threshold is intentionally 0% until real unit tests are added.

Recommended approach

1. Add unit tests for hooks (e.g. `useStreamingChat` coverage is partial)
2. Add unit tests for pure utility/helper functions
3. Raise thresholds in `services/admin/vitest.config.spec.ts` incrementally as tests are added

How to check progress

```bash
pnpm --filter admin test:coverage
```