fix(infra): wait for postgres readiness before running migrations on container start

Installs postgresql-client in the dev image so pg_isready is available.
The startup script now polls until postgres accepts connections, preventing
the P1001 "can't reach database" crash when the app container starts before
postgres is fully ready.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile.dev

@@ -1,7 +1,7 @@
 FROM node:20-bookworm-slim AS base
 
 # Prisma needs OpenSSL available during install/generate/runtime.
-RUN apt-get update -y && apt-get install -y openssl && rm -rf /var/lib/apt/lists/*
+RUN apt-get update -y && apt-get install -y openssl postgresql-client && rm -rf /var/lib/apt/lists/*
 
 # Install pnpm
 RUN npm install -g pnpm@9.14.2