Expose the active weekly subscription window through /v1/usage, calculate offsets with the same normalized page size used by queries, and keep user-facing date ranges on the browser's local calendar date.
Constraint: Preserve existing response fields and avoid new dependencies
Rejected: Keep duplicate inline date formatters | a shared local-date utility prevents the same UTC regression in both views
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Keep Offset and Limit based on the same normalized page size
Tested: go test ./internal/pkg/pagination ./internal/handler; go vet ./internal/pkg/pagination ./internal/handler; frontend 923 tests; pnpm typecheck; pnpm lint:check; pnpm build
Not-tested: Live API request against a deployed subscription
Related: #4121
Route direct fetch calls, setup requests, gateway usage checks, and ops WebSocket connections through the configured API base instead of assuming same-origin backend paths.
Also derive OAuth callback suggestions from the configured API base so split frontend/API deployments show usable redirect URLs.
yan9651688