feat: Trade Matching & Suggestions module

[devIKargi]

Closes #27

Body

Summary

Adds a lightweight trade matching system that ranks compatible listings for a given listing and lets users propose trades directly from the marketplace.

What's included

Matching algorithm (src/services/matchService.ts)

• Scores candidates on three dimensions: category (40 pts), tag overlap via Jaccard similarity (35 pts), and value proximity (25 pts)
• Excludes same-seller, inactive, and self-matches
• Surfaces only matches above a configurable threshold, ranked by score

UI components

• SuggestedMatches — displays ranked match cards with score breakdown bars, human-readable reasons, and a "Propose trade" action with optional message
• ListingCard — new "Find matches" button per listing
• ListingCreate — new tags input (Enter to add, clickable chips)
• MarketplaceClient — "matches" view with back-navigation

Types & data (src/types/listing.ts)

• Added tags: string[] to Listing
• New types: MatchSuggestion, TradeMatchResult, TradeProposal, TradeProposalStatus
• Seed data enriched with descriptive tags for all 5 listings

Proposal management (localStorage-backed)

• proposeTrade, acceptProposal, declineProposal, getProposalsForListing

Analytics

• Tracks listing_view (when viewing matches) and match_propose events via existing useAnalytics hook

Tests (src/services/__tests__/matchService.unit.test.ts)

• 23 unit tests covering scoreCategory, scoreTags, scoreValue, and findMatches — including exclusion logic, ranking, breakdown integrity, and edge cases

Files changed (9 files, +954 / -13)

File	Change
src/types/listing.ts	tags on Listing, new match/proposal types
src/services/matchService.ts	Matching algorithm + proposal CRUD
src/services/listingService.ts	Tags in seed data
src/components/SuggestedMatches.tsx	Match display + propose flow
src/components/MarketplaceClient.tsx	Matches view routing
src/components/ListingCard.tsx	"Find matches" button
src/components/ListingList.tsx	Pass onFindMatches prop
src/components/ListingCreate.tsx	Tags input
src/services/__tests__/matchService.unit.test.ts	23 unit tests

Verification

• ✅ next build — compiled successfully
• ✅ tsc --noEmit — zero type errors
• ✅ next lint — no warnings or errors
• ✅ jest — 125/125 tests pass (13 suites)