Add security warnings for default passwords in env.template

Co-authored-by: Sulstice <11812946+Sulstice@users.noreply.github.com>

Author: Copilot

env.template

@@ -8,6 +8,7 @@
 # ----------------------------------------------------------------------------
 # PostgreSQL Database Configuration
 # ----------------------------------------------------------------------------
+# WARNING: Change these default passwords in production!
 POSTGRES_USER=postgres
 POSTGRES_PASSWORD=postgres
 POSTGRES_DB=brainkb
@@ -30,6 +31,7 @@ DB_PORT=5432
 DJANGO_SUPERUSER_USERNAME=admin
 DJANGO_SUPERUSER_EMAIL=admin@brainkb.org
 DJANGO_SUPERUSER_PASSWORD=admin
+# WARNING: Change this secret key in production! Use Django's get_random_secret_key()
 BRAINYPEDIA_APITOKEN_MANAGER_SECRET_KEY=django-insecure-default-key-change-in-production
 
 # ----------------------------------------------------------------------------
@@ -56,6 +58,7 @@ JWT_ALGORITHM=HS256
 # ----------------------------------------------------------------------------
 # Each service has its own JWT secret key to prevent tokens from one service
 # from being used to authenticate with another service
+# WARNING: Change these JWT secret keys in production! Use strong random values
 QUERY_SERVICE_JWT_SECRET_KEY=query-service-jwt-secret-key-default
 ML_SERVICE_JWT_SECRET_KEY=ml-service-jwt-secret-key-default
 
@@ -80,6 +83,7 @@ PGADMIN_PORT=5051
 # ----------------------------------------------------------------------------
 # Oxigraph SPARQL Database Configuration
 # ----------------------------------------------------------------------------
+# WARNING: Change these default passwords in production!
 OXIGRAPH_USER=admin
 OXIGRAPH_PASSWORD=admin
 
@@ -106,6 +110,7 @@ WEB_CONCURRENCY=6
 # ----------------------------------------------------------------------------
 # pgAdmin Configuration (Optional - for PostgreSQL management)
 # ----------------------------------------------------------------------------
+# WARNING: Change these default passwords in production!
 PGADMIN_DEFAULT_EMAIL=admin@brainkb.org
 PGADMIN_DEFAULT_PASSWORD=admin
 PGADMIN_SERVER_NAME=BrainKB PostgreSQL