BLAST Results interactions batch

Motivation

Two more deferred items are now code-verifiable: switching result tabs always dumped the user back to the top, and the degraded job-listing notice had no way to retry without a full reload.

User-facing change

• #21 Per-tab scroll restore — each result tab remembers its window scroll position; returning to a tab restores where you were instead of jumping to the top. The Run details tab is excluded so its live-log tail-follow keeps ownership of scroll.
• #40 Degraded retry — when the BLAST job listing is degraded, the notice now shows a Retry button that re-runs the listing query (spinner while in flight).

Code change summary

• web/src/pages/BlastResults.tsx: a scrollByTabRef records the active tab's scroll on every scroll event; a second effect restores the saved position (via requestAnimationFrame) on tab change, skipping the run tab.
• web/src/pages/BlastJobs/JobsEmptyState.tsx: NoJobsEmpty accepts onRetry / retrying and renders a Retry button into the DegradedNotice action slot.
• web/src/pages/BlastJobs/BlastJobs.tsx: passes onRetry={() => jobsQuery.refetch()} + retrying={jobsQuery.isFetching}.

Validation evidence

• cd web && npm run build → clean.
• cd web && npm test -- --run BlastJobs blastJobs → 19 passed.
• npx eslint on the three changed files → clean.

No backend / API / IaC changes.