Update SAAC_DEPLOYMENT.md: template_db → postgres

SAAC_DEPLOYMENT.md

@@ -74,10 +74,10 @@ services:
   app:
     environment:
       # Must match POSTGRES_DB below!
-      - DATABASE_URL=postgresql://postgres:postgres@postgres:5432/template_db
+      - DATABASE_URL=postgresql://postgres:postgres@postgres:5432/postgres
   postgres:
     environment:
-      - POSTGRES_DB=template_db  # This creates the database
+      - POSTGRES_DB=postgres  # This creates the database
 ```
 
 **WARNING:** If you change `POSTGRES_DB` after first deploy, the old name persists in the Docker volume. The new name won't exist. Either keep the original name or destroy and recreate the postgres volume.