Configure Prisma datasource URLs and add optimized indexes

[gouthamf22labs]

1. Configure Prisma datasource URLs for docker compose build fix and add optimized indexes for Contact by setting url, directUrl, and shadowDatabaseUrl in schema.prisma to use environment variables, and introducing composite/covering indexes on Contact(instanceId, remoteJid) (including id) to improve query performance and support efficient index-only scans.