chore: update PostgreSQL host in .env-sample and volume path in docker-compose.yml for Docker deployment

.env-sample

@@ -39,7 +39,7 @@ PUBLIC_METRICS_API=False # Set to True to allow public access to the metrics API
 #   - Data corruption risks under heavy load
 # For production deployments, use PostgreSQL!
 DATABASE_TYPE=postgresql # Options: sqlite, postgresql - Use postgresql for production, sqlite for development only
-DATABASE_URL=comet:comet@localhost:5432/comet # For PostgreSQL (user:password@host:port/database)
+DATABASE_URL=comet:comet@postgres:5432/comet # For PostgreSQL (user:password@host:port/database)
 DATABASE_PATH=data/comet.db # Only relevant for SQLite (development only)
 DATABASE_BATCH_SIZE=20000 # The batch size for the database import and export operations
 DATABASE_READ_REPLICA_URLS='' # Optional JSON array of PostgreSQL read-only URLs, e.g. '["user:pass@replica-1/db", "user:pass@replica-2/db"]'

deployment/docker-compose.yml

@@ -51,7 +51,7 @@ services:
       - "-c"
       - "max_connections=100"
     volumes:
-      - postgres_data:/var/lib/postgresql/docker
+      - postgres_data:/var/lib/postgresql/18/docker
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U comet -d comet"]
       interval: 5s