feat(backend): prisma singleton + updateMarketStatus service (#880 #884)

[darcszn]

---

Changes

Issue #880 — Prisma Singleton (src/db.ts)

Problem: `src/db.ts` exported a bare `new PrismaClient()` with no singleton guard. In development, `ts-node-dev` hot-reloads modules on every file save, which would instantiate a new `PrismaClient` on each reload — exhausting the PostgreSQL connection pool quickly.

Additionally, `src/lib/prisma.ts` and `src/lib/db.ts` each created their own independent `PrismaClient` instances, meaning the app could silently run with 3 separate connection pools.

Fix:

• Rewrote `src/db.ts` to use a `globalThis.__prisma` guard. In non-production environments, the instance is stored on `globalThis` so hot-reloads reuse the existing connection instead of spawning a new one. Production always creates a fresh instance on startup.
• Configured `PrismaClient` log levels: `query + warn + error` in development, `warn + error` in production.
• Consolidated `src/lib/prisma.ts` and `src/lib/db.ts` to re-export from the canonical `src/db.ts` singleton rather than each owning their own client.

```ts
// src/db.ts
export const db: PrismaClient =
globalThis.__prisma ?? new PrismaClient({ log: [...] });

if (process.env.NODE_ENV !== 'production') {
globalThis.__prisma = db;
}
```

Acceptance criteria met:

• `import { db } from './db'` works in any service file — all existing services (`market.service.ts`, `bet.service.ts`, `resolution.service.ts`) already use this import and continue to work unchanged.
• `npm run db:migrate` and `npm run db:generate` scripts were already wired correctly in `package.json`.
• Prisma schema was already complete and correct with all models, enums, and relations.

---

Issue #884 — `updateMarketStatus()` (src/services/market.service.ts)

Problem: The service file had several bugs that would cause runtime crashes:

1. Duplicate `createMarketRecord` declaration — A broken first version of the function (referencing an undefined `txHash` variable) was left above the correct transactional implementation, causing a TypeScript compile error.
2. Undefined `prisma` variable — `resolveMarket()`, `cancelMarket()`, and `resolveMarketDispute()` all called `prisma.market.update()` and `prisma.adminLog.create()`, but `prisma` was never imported or defined. These functions would throw `ReferenceError: prisma is not defined` at runtime.
3. `pagination?.limit` mismatch — `getAllMarkets()` and `getMarketLeaderboard()` accessed `pagination?.limit` but the `Pagination` interface defines the field as `pageSize`, causing silent `undefined` fallbacks on every paginated call.
4. String literal status check — `updateMarketStatus()` used the string `'Resolved'` for the `resolvedAt` guard instead of the `MarketStatus.Resolved` enum value.

Fix:

• Removed the duplicate broken `createMarketRecord` declaration entirely.
• Replaced all `prisma.` calls with `db.` throughout `resolveMarket`, `cancelMarket`, and `resolveMarketDispute`.
• Fixed `pagination?.limit` → `pagination?.pageSize` in both `getAllMarkets` and `getMarketLeaderboard`, and capped the limit at `MAX_PAGE_SIZE`.
• Hardened the `resolvedAt` condition in `updateMarketStatus` to use `MarketStatus.Resolved` enum value.

```ts
export async function updateMarketStatus(
market_id: string,
status: MarketStatus,
outcome?: Outcome
): Promise {
return db.market.update({
where: { id: market_id },
data: {
status,
...(outcome !== undefined && { outcome }),
...(status === MarketStatus.Resolved && { resolvedAt: new Date() }),
},
});
}
```

Acceptance criteria met:

• Status updated correctly for all `MarketStatus` values (Open, Locked, Resolved, Cancelled, Disputed).
• `resolvedAt` is set precisely when `status === MarketStatus.Resolved`.
• `outcome` is stored when provided, omitted when not.
• `resolveMarket`, `cancelMarket`, and `resolveMarketDispute` now correctly call `db` and will no longer throw at runtime.

---

Files Changed

File	Change
`backend/src/db.ts`	Rewritten — proper singleton with `globalThis` guard and log config
`backend/src/lib/prisma.ts`	Consolidated — re-exports singleton from `../db`
`backend/src/lib/db.ts`	Consolidated — re-exports singleton from `../db`
`backend/src/services/market.service.ts`	Fixed duplicate declaration, `prisma` → `db`, pagination field, enum guard

closes #880
closes #884