fix: repair merge-corrupted files and restore CI

[Markodiba]

Summary

• Repairs several files that had duplicate/interleaved code left behind by bad merges, breaking tsc, npm test, and npm run build:
  • lib/stellar.ts — missing closing brace between two functions
  • app/error.tsx — two competing error-parsing helpers spliced together
  • components/layout/testnet-faucet-banner.tsx — two full component implementations concatenated; kept the current Friendbot-funding version
  • app/app/analytics/page.tsx and components/analytics/charts.tsx — reconstructed from git history by replaying the legitimate SECONDS_PER_DAY and per-token-decimals fixes onto the last known-good version, dropping dead code pulled in by mistake
• Fixes stale/broken tests uncovered once those files could compile again:
  • Deletes use-bulk-actions.test.ts / use-bulk-select.test.ts, which tested hooks deliberately removed as dead code long before a stale PR re-added tests for them
  • Fixes missing TokenInfo.address / StreamData.linearAmount+duration fields, a missing afterEach import, and a nonexistent toEndWith matcher in test fixtures
  • Updates webhook-settings tests to check the inline field errors the component renders now, instead of the toast calls it used before a later, deliberate UX fix
  • Fixes a real bug in useTokenPrice/usePortfolioValue: an empty stream list returned totalUsd=null instead of 0, and the price cache's error fallback never actually restored the last known-good price into a new component instance
  • Fixes module-level price-cache leakage between tests via vi.resetModules() + dynamic import, matching the pattern already used elsewhere in this repo
  • Fixes flaky act()/fake-timer interactions in use-auto-withdraw and use-contract tests
• Documents NEXT_PUBLIC_STELLAR_NETWORK in .env.local.example and DEPLOYMENT.md, which picks the network but was previously undocumented

Test plan

• npm run lint — 0 errors
• npx tsc --noEmit — 0 errors
• npm test — 607/607 passing across 36 files
• npm run build — succeeds
  closes Document NEXT_PUBLIC_STELLAR_NETWORK in .env.local.example and DEPLOYMENT.md #520