Coalesce in-flight fantasy analysis and harden refresh cache bypass

[Copilot]

Refresh requests in the fantasy overview path could still duplicate concurrent AI generations and might not bypass HTTP/browser caches despite refresh=true. This PR closes both gaps in backend cache behavior and frontend refresh fetch semantics.

• Backend: analysis cache concurrency + stale-entry handling

  • Added an in-flight promise cache keyed with the same analysis key used by analysisCache.
  • getTradeAnalysis(...) now:
    • returns fresh cached data when valid,
    • deletes expired cache entries on access,
    • reuses existing in-flight generation for identical concurrent requests.

• Frontend: guaranteed network refresh

  • Refresh calls in useFantasy now pass cache: 'no-store' with the existing ?refresh=true URL to prevent intermediary/browser cache reuse.

• Coverage updates for new behavior

  • Added focused spec coverage for:
    • concurrent coalescing to a single generate() invocation,
    • stale analysis eviction/regeneration,
    • refresh fetch options including cache: 'no-store'.

const inFlight = this.analysisRequests.get(key);
if (inFlight) return inFlight;

const request = generate()
  .then((analysis) => {
    this.analysisCache.set(key, { expiresAt: Date.now() + AI_ANALYSIS_CACHE_MS, analysis });
    return analysis;
  })
  .finally(() => this.analysisRequests.delete(key));

[Copilot]

🟢 Approval recommended

The changes are localized, align with the PR’s stated goals, and include targeted test coverage for the new cache/concurrency behaviors.

Pull request overview

This PR tightens “refresh” behavior for the fantasy overview by (1) preventing duplicate concurrent AI trade-analysis generations on the backend via in-flight request coalescing and (2) ensuring frontend refresh requests bypass intermediary/browser caches by explicitly using cache: 'no-store'.

Changes:

• Backend: added an in-flight promise map to reuse an ongoing generateTradeAnalysis(...) for identical concurrent requests, while also deleting expired cached entries on access.
• Frontend: refresh requests now pass RequestInit.cache = 'no-store' alongside the existing ?refresh=true query param.
• Tests: added/updated focused specs to validate refresh fetch options, stale cache eviction/regeneration, and concurrent-request coalescing.

File summaries

File	Description
packages/frontend/src/pages/FantasyPage.spec.tsx	Asserts refresh fetch calls include { cache: 'no-store' }.
packages/frontend/src/hooks/useFantasy.ts	Passes { cache: 'no-store' } for refresh overview requests to force a network fetch.
packages/backend/src/fantasy/fantasy.service.ts	Coalesces concurrent analysis generation via analysisRequests and clears expired cache entries.
packages/backend/src/fantasy/fantasy.service.spec.ts	Adds test coverage for concurrent coalescing and expired-entry regeneration behavior.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Lite

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