chore(env): split dev/prod env files and clarify keycloak settings

scripts/start_dev.sh

@@ -3,12 +3,9 @@ set -euo pipefail
 
 cd "$(dirname "$0")/.."
 source .venv/bin/activate
-if [ -f ".env.development" ]; then
-  ENV_FILE=".env.development"
-elif [ -f ".env" ]; then
-  ENV_FILE=".env"
-else
-  echo "missing .env.development or .env. copy .env.example first."
+ENV_FILE=".env.development"
+if [ ! -f "$ENV_FILE" ]; then
+  echo "missing $ENV_FILE."
   exit 1
 fi