feat(01-01): NestJS API with health endpoint and Prisma schema

- NestJS app with ConfigModule and HealthModule
- GET /health endpoint returning {status, timestamp} using HealthResponse type
- Prisma schema with PostgreSQL datasource and Tenant model (multi-tenancy foundation)
- Multi-stage Dockerfile with non-root nestjs user, monorepo root as build context
- Workspace dependency on @tessera/shared for shared types
- Type-check passes successfully

apps/api/Dockerfile

@@ -0,0 +1,30 @@
+FROM node:24-alpine AS base
+RUN corepack enable && corepack prepare pnpm@9 --activate
+
+FROM base AS deps
+WORKDIR /app
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
+COPY apps/api/package.json ./apps/api/
+COPY packages/shared/package.json ./packages/shared/
+RUN pnpm install --frozen-lockfile --filter=@tessera/api...
+
+FROM base AS builder
+WORKDIR /app
+COPY --from=deps /app/ ./
+COPY apps/api/ ./apps/api/
+COPY packages/shared/ ./packages/shared/
+COPY tsconfig.base.json ./
+RUN pnpm --filter=@tessera/api build
+
+FROM node:24-alpine AS runner
+WORKDIR /app
+ENV NODE_ENV=production
+RUN addgroup --system --gid 1001 nestjs && \
+    adduser --system --uid 1001 nestjs
+COPY --from=builder /app/apps/api/dist ./dist
+COPY --from=builder /app/apps/api/node_modules ./node_modules
+COPY --from=builder /app/apps/api/package.json ./
+COPY --from=builder /app/node_modules/.pnpm ./node_modules/.pnpm
+USER nestjs
+EXPOSE 3001
+CMD ["node", "dist/main.js"]