Drop 9 hand-rolled apiFetch calls with redundant Content-Type
headers + manual JSON.stringify. The api.* wrapper in client.ts
already handles both. Identical wire shape; existing tests cover
all endpoints.
Also makes api.del generic so DELETE endpoints with typed returns
(playlist track removal) can use the wrapper instead of raw
apiFetch. Default `T = null` preserves existing callers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>