v1.5.4

What's changed

• fix(request): replace silent error swallowing with proper error propagation
• fix(request): remove unreachable switch cases comparing HTTP status codes against LastFM API error codes
• fix(request): parse JSON body and throw on LastFM API error codes (2–29)
• fix(types): correct chart response shapes to match live LastFM API
• refactor(request): rewrite .then/.catch chain as clean async/await
• test(request): add error handling tests covering HTTP errors, LastFM API errors, and network failures
• test(api): add integration tests for all previously untested methods