Feat/api versioning v1

[sweetesty]

Closes #260

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This PR adds /api/v1/ versioning to all routes, resolves all compiler and IDE errors surfaced during migration, and validates the versioned routes with a full passing test suite.

Route versioning

• All API routes moved under /api/v1/ prefix in the Next.js app/api/v1/ directory
• Old unversioned routes return 301 Moved Permanently redirects to their /api/v1/ equivalents
• All frontend API call URLs updated to /api/v1/ paths — no unversioned URLs remaining
• README.md updated with API versioning strategy, current version, and redirect behaviour for legacy URLs

Compiler & IDE fixes resolved during migration

1. Missing Dispute types — Dispute interface and DisputeStatus type added to src/types/index.ts; was causing errors in admin components and services
2. React Query implicit any — err parameter in CircleChat.tsx mutation onError callback explicitly cast as Error
3. Missing state in JoinCircleForm.tsx — noSavedKey / setNoSavedKey state declaration was absent; added via useState(false)
4. Payout type resolution — PayoutHistoryRow interface extracted to @/types/index.ts to resolve compiler failures on dynamic route imports in PayoutHistory.tsx and the payouts route
5. NextAuth session.user.id type errors — session.user safely cast as { id: string } | undefined across 5 route files (approve, reject, pending-requests, contribute/verify, leave). Note: this pattern repeating across routes is a candidate for consolidation into a next-auth.d.ts session type extension as a follow-up
6. userId used before declaration in join/route.ts — latent runtime bug surfaced by the migration; fixed at the declaration site
7. Zod validation in tests — circle-1 test string replaced with a valid UUID; Stellar public key and HTTPS horizonUrl mocked to satisfy SDK validation
8. CreateCircleForm test isolation — replaced fragile mockResolvedValueOnce with a mockImplementation that cleanly intercepts background FX rate queries on mount, preventing mock assertion interference on form submissions

Test suite — 4/4 suites passing

• src/app/api/v1/circles/[id]/join/__tests__/route.test.ts
• src/app/api/v1/circles/[id]/contribute/__tests__/route.test.ts
• src/app/api/v1/circles/[id]/contribute/verify/__tests__/route.test.ts
• src/components/circle/__tests__/CreateCircleForm.test.tsx

Acceptance criteria met:

• ✅ All routes moved under /api/v1/
• ✅ Old routes return 301 redirect to versioned routes
• ✅ API version documented in README
• ✅ Frontend updated to use versioned URLs

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[JosephOnuh]

resolve conflicts please

[sweetesty]

@JosephOnuh done