chore: update deployment config

.env.example

@@ -1,10 +1,10 @@
 # Copy to .env for local deployment.
 # Generate SECRET_KEY with: python -c "import secrets; print(secrets.token_hex(32))"
-SECRET_KEY=
+SECRET_KEY=change-me-to-a-long-random-secret
 
 # Required for first deployment. Used to create or rotate the admin account on startup.
 ADMIN_USERNAME=admin
-ADMIN_PASSWORD=
+ADMIN_PASSWORD=change-me
 
 # Persist the app database in the mounted ./data directory.
 DATABASE_URL=sqlite:////app/data/pipe_survival_0331.db