Demo: fix stopping Docker

[johnnyomair]

The change in #5297 causes Docker to fail when stopping the demo-docker process:

demo-docker:  Compose Stopping Gracefully Stopping... press Ctrl+C again to force
demo-docker: got 3 SIGTERM/SIGINTs, forcefully exiting
demo-docker:  ELIFECYCLE  Command failed with exit code 1.
demo-docker: [dev-pm] process stopped

According to Claude, this is related to PNPM's shutdown handling.
The only workaround I (and Claude) could find was to not use PNPM and dotenv.
Then Docker can shutdown gracefully:

demo-docker:  Compose Stopping Gracefully Stopping... press Ctrl+C again to force
demo-docker:  Container core-v9-postgres-1 Stopping 
demo-docker:  Container core-v9-jaeger-1 Stopping 
demo-docker:  Container core-v9-imgproxy-1 Stopping 
demo-docker:  Container core-v9-mailpit-1 Stopping 
demo-docker:  Container core-v9-valkey-1 Stopping 
demo-docker:  Container core-v9-jaeger-1 Stopped 
demo-docker:  Container core-v9-imgproxy-1 Stopped 
demo-docker:  Container core-v9-postgres-1 Stopped 
demo-docker:  Container core-v9-valkey-1 Stopped 
demo-docker:  Container core-v9-mailpit-1 Stopped 
demo-docker: 
demo-docker: [dev-pm] process stopped

[johnnyomair]

This change fixes the following error:

demo-docker: .env: line 114: offline_access: command not found

[nsams]

.env is always there

Suggested change

	script: "set -a; [ -f .env ] && . .env; [ -f .env.local ] && . .env.local; [ -f .env.secrets ] && . .env.secrets; set +a; docker compose up",
	script: "set -a; . .env; [ -f .env.local ] && . .env.local; [ -f .env.secrets ] && . .env.secrets; set +a; docker compose up",

and since https://github.com/vivid-planet/comet/blob/main/install.sh#L9 even .env.local always exists, so maybe it could even be simplified to:

Suggested change

	script: "set -a; [ -f .env ] && . .env; [ -f .env.local ] && . .env.local; [ -f .env.secrets ] && . .env.secrets; set +a; docker compose up",
	script: "set -a; . .env; . .env.local; . .env.secrets; set +a; docker compose up",

[johnnyomair]

Updated. Also, removed support for .env.secrets as it doesn't make sense too me.