Self-hosted: `firecrawl --status` and `config --api-url` treat setup as unauthenticated

### Problem
For self-hosted users, CLI still behaves like cloud auth is required.

### Repro
1. Ensure credentials file does not exist (first-time setup):
- macOS: `~/Library/Application Support/firecrawl-cli/credentials.json`
2. Run:
```bash
firecrawl config --api-url http://localhost:3002
```
3. CLI enters cloud login flow (`1/2`) and empty key fails.
4. `credentials.json` is not auto-created with `apiUrl` during this first-time self-hosted setup path.

Then:
```bash
firecrawl --status
```
shows:
- `Not authenticated`
- `Run 'firecrawl login' to authenticate`

### Expected
- `config --api-url ` should save URL without forcing login.
- If `credentials.json` does not exist, `config` should create it and persist `apiUrl`.
- `--status` should show self-hosted configured/ready state (not unauthenticated).
- No `Authorization: Bearer undefined` header when self-hosted has no API key.

### Note
Under the same self-hosted setup, `firecrawl credit-usage` can succeed, while `firecrawl --status` still reports unauthenticated.

### Impact
Firecrawl skill uses `--status` to detect CLI readiness; this blocks self-hosted skill usage.