Add Pro-gated sample reanalysis (single + batch/all)

Commit notes

Adds POST /samples/:id/reanalyse and POST /samples/batch/reanalyse endpoints that re-enqueue the audio analysis job for owned samples, gated to Pro/Team subscription plans. Wires up matching API client functions, TanStack Query mutations, and library UI controls (per-row reanalyse button, "Reanalyse" for selection, "Reanalyse All").

[private session redacted]