Feat: Generate TypeScript API client from OpenAPI spec

[Lansa-18]

Closes #118

Feat: Generate Typed TypeScript HTTP Client from OpenAPI Spec #118

Summary

Generates a fully typed TypeScript HTTP client from the NestJS Swagger/OpenAPI spec and wires it into the frontend, replacing raw fetch calls with compile-time–safe URL and request-body checking.

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Backend

• Extracts DocumentBuilder config into src/swagger.config.ts
• Adds scripts/export-spec.ts — bootstraps NestJS without an HTTP listener and writes openapi.json to the frontend directory; registered as npm run spec:export
• Fixes missing @ApiBody decorators on verification-inbox.controller.ts (approve, reject, requestResubmission, addInternalNote) — bodies were accepted at runtime but invisible in the spec
• Adds additionalProperties: true to the metadata field in CreateCampaignDto / UpdateCampaignDto so the generated types produce Record<string, unknown> instead of Record<string, never>

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Frontend

• Adds openapi-fetch (runtime client) and openapi-typescript (codegen) as dependencies; pnpm generate:api regenerates src/lib/generated/api.ts from openapi.json
• Commits openapi.json and src/lib/generated/api.ts (do not edit by hand)
• Adds src/lib/api-client.ts — createClient<paths> routed through the existing fetchClient mock layer so NEXT_PUBLIC_USE_MOCKS=true continues to work transparently
• Migrates useCampaigns, useHealthStatus, useOptimisticCampaignMutations, verification-api, verification-inbox-api, and AidDistributionMap to the typed client
• Fixes pre-existing URL prefix bugs uncovered during migration: hooks were calling /campaigns, /health, /verification-inbox etc. without the required /api/v1/ prefix
• useAidPackages and csv-validation (/recipients/import/*) intentionally kept on raw fetchClient — these endpoints are mock-only and absent from the backend Swagger spec

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CI

Adds two steps after Build in backend-ci.yml: re-runs spec:export, then git diff --exit-code app/frontend/openapi.json to fail the pipeline if the committed spec has drifted from the backend.

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Maintainer Notice — Pre-existing Frontend Routing Issue (out of scope for this PR)

While smoke-testing the frontend during this PR, a pre-existing issue was found that prevents the frontend from rendering at all on main.

The root layout (src/app/layout.tsx) calls getMessages() from next-intl/server outside the [locale] route segment. Without a locale middleware to inject the locale into the request context, getRequestConfig receives requestLocale = undefined, hits the notFound() guard in src/i18n.ts, and every page returns 404. Additionally, Next.js 16 (used by this project) has renamed middleware.ts to proxy.ts, so the old convention no longer applies.

The fix is: (1) add proxy.ts at app/frontend/proxy.ts using next-intl/middleware's createMiddleware for locale detection and redirect, and (2) move getMessages() and NextIntlClientProvider from the root layout into src/app/[locale]/layout.tsx where locale context is available.

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Testing

# Backend — export spec, unit tests, lint
cd app/backend
DATABASE_URL="file:./prisma/dev.db" npm run spec:export   # openapi.json written
npm test                                                   # all unit tests pass
npm run lint:check                                         # no errors in changed files

# Frontend — regenerate types, type-check, tests, lint
cd app/frontend
pnpm generate:api      # src/lib/generated/api.ts regenerated in 42ms
pnpm tsc --noEmit      # 0 type errors
pnpm test              # 82 tests pass across 9 suites

Manual verification:

• Backend started (npm run start:dev) and Swagger UI confirmed live at http://localhost:3000/api/docs — all tag groups visible (Analytics, Campaigns, Verification Inbox, etc.)
• Mock API tests (mock-api/client.test.ts) confirm the fetchClient interception layer still works through apiClient when NEXT_PUBLIC_USE_MOCKS=true

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Checklist

• Tests added or updated for new/changed behavior
• Existing tests pass
• No secrets, keys, or seed phrases committed
• Follows the coding conventions in the relevant service README
• PR is focused on a single concern

[Lansa-18]

@kilodesodiq-arch Kindly review.

[kilodesodiq-arch]

Thanks @Lansa-18 — solid generated TS client with proper types. Backend CI is green and this resolves #118 cleanly. Merging now.