Process Compose Module Implementation

1. Defines stackpanel.process-compose.{enable, processes, environment, package}
2. Auto-generates process entries from apps (defaults to turbo run -F <name> dev)
3. Creates a `dev` wrapper package added to devshell

# All apps get a dev process by default using: turbo run -F <name> dev
# Just define the app:
web = {
  path = "apps/web";
};

# Override with explicit command if needed:
api = {
  path = "apps/api";
  tasks.dev.command = "go run ./cmd/api";
};

# Disable process-compose for a specific app:
stackpanel.apps.legacy.process-compose.enable = false;

config.stackpanel.process-compose.processes
config.stackpanel.process-compose.package