feat: live TVL and user metrics with 24h sparkline and /api/stats

[ijeoma270]

Closes #7

What changed

New files

File	Purpose
src/lib/stats.ts	fetchStats() — data layer; queries factory contract (stubbed with TODO for when it's deployed), falls back to realistic demo data; exports StatsData type
src/app/api/stats/route.ts	GET /api/stats with 60-second Next.js revalidation — all clients share one cached response
src/hooks/useStats.ts	useStats() react-query hook; polls every 60 s; tries /api/stats first, falls back to direct fetchStats() call so it works in static export too
src/components/Sparkline/Sparkline.tsx	Dependency-free SVG sparkline with area fill and latest-point dot

Modified files

• src/app/page.tsx — replaces hardcoded 30,738 / $302M / 213 with live data from useStats(); adds Chakra skeleton loading state; Demo badge (with tooltip explaining contracts not yet deployed) on the TVL card; 24h SVG sparkline inline with TVL value; third panel swapped to "Last Updated" with relative-time label (just now, 2m ago, …)
• next.config.ts — output: "export" now conditional on NEXT_EXPORT=true; unset = server mode, API routes active (Vercel / next start)
• .github/workflows/deploy-github-pages.yml — adds NEXT_EXPORT: "true" to the build step so GitHub Pages CI still produces the static out/ directory

Architecture

Browser / polling every 60 s
       │
       ▼
useStats (react-query, staleTime 60 s)
       │
       ├─ tries GET /api/stats  (server deployment: Vercel / next start)
       │         │
       │         └─ fetchStats()  ← stubbed Soroban RPC + demo fallback
       │              └─ revalidate: 60 (Next.js cache)
       │
       └─ falls back to fetchStats() directly (static GitHub Pages export)

Wiring real data

When the factory contract is deployed, replace the TODO block in src/lib/stats.ts with:

// 1. Enumerate pools
const poolIds = await invokeView(rpc, factoryId, "get_pools", [])
// 2. Aggregate locked amounts per pool
// 3. USD conversion via Stellar DEX order book
// 4. Count unique stakers
// Then return source: "live"

The Demo badge and its tooltip disappear automatically once source: "live" is returned.

How to test

npm run dev          # server mode — /api/stats active, metrics update every 60s
NEXT_EXPORT=true npm run build  # static export — builds out/ without API routes
npm run build        # server build — /api/stats shows Revalidate: 1m in output
npx tsc --noEmit     # passes clean

[prodbycorne]

Let me review.