Add price-drop and status alerts for watchlisted marketplace listings

[1nonlypiece]

📌 Description

Even with a watchlist, users won't notice when a saved listing's price changes or it sells. There is no alerting on the marketplace surfaces.

This issue adds price-drop and status-change alerts for watchlisted listings, surfaced via the existing toast/notification system.

🎯 Requirements and Context

This is a feature / enhancement task for the CommitLabs frontend (Next.js + TypeScript). It must be implemented cleanly, fully typed, accessible, and well tested — and must not regress existing behavior.

• Detect price decreases and sold/removed transitions for watched listings against last-seen state.
• Surface alerts through ToastProvider and/or the notifications center without spamming (dedupe).
• Let the user mute alerts per listing; persist mute state.
• Polling must be efficient and abortable; no tight loops.

🛠️ Suggested Execution

1. Fork the repo and create a branch

git checkout -b feature/watchlist-price-alerts

2. Implement the change

• Primary files to add or modify:
  • src/components/marketplace/WatchlistAlerts.tsx — detection + dispatch.
  • src/components/toast/ToastProvider.tsx — reuse dispatch.
  • src/app/api/marketplace/listings/route.ts — read listing data.
• Add focused tests in src/components/marketplace/WatchlistAlerts.test.tsx using Jest / Vitest + React Testing Library (happy-dom), covering rendering, interaction, and the edge cases below.
• Add documentation in docs/WATCHLIST_ALERTS.md describing the feature, props/API, accessibility behavior, and a usage example; cross-link it from the relevant README/docs.
• Keep the diff small and reviewer-friendly; reuse existing primitives, hooks, and the typed API client instead of duplicating logic.

3. Cover edge cases

• price drop triggers one alert
• sold transition alert
• mute suppresses alerts
• dedupe avoids repeats

4. Test and commit

• Run the suite (e.g. pnpm test / pnpm vitest run) and ensure new lines are covered.
• Verify keyboard navigation, focus handling, and prefers-reduced-motion where relevant.

Example commit message

feat: price-drop and status alerts for watchlisted listings

✅ Guidelines

• Minimum 95% test coverage on the new/changed lines.
• Clear, reviewer-friendly documentation (props/API + usage example + accessibility notes).
• No regressions to existing components, routes, or tests.
• Fully typed (no any), accessible (labels, roles, live regions where relevant).
• Timeframe: 96 hours.

🏷️ Labels

type-feature · type-enhancement · area-frontend · MAYBE REWARDED · GRANTFOX OSS · OFFICIAL CAMPAIGN

💬 Community & Support

• Join the CommitLabs contributor Discord to coordinate, ask questions, and get unblocked fast: https://discord.gg/WV7tdYkJk
• Please introduce yourself in the channel before you start so we can avoid duplicate work, pair you with a reviewer, and get your PR merged quickly.
• Maintainers actively triage this channel and aim for fast, clear, respectful reviews — reach out any time you're blocked.

[mikewheeleer]

I would like to work on this issue, and I have good knowledge of smart contacts and Sorabani Rust. Kindly assign it to me.