fix(cache): drain workout range pagination

[garrettladley]

• drains whoop next_token pages before returning workout range results
• drains repository cursors before treating cached range data as complete
• applies cursor draining to workout, cycle, sleep, calendar, and historical cache reads
• adds regression coverage for api pagination and cache cursor draining with t.Context() and t.Helper()

[codecov]

Codecov Report

❌ Patch coverage is 33.80282% with 47 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/cache/service.go	33.80%	42 Missing and 5 partials ⚠️

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