Refactored to maintain a separate cloud version

Moves 12 packages from internal/ to pkg/ (config, id, validate, events, db,
auth, lifecycle, scheduler, channels, audit, service) so they can be imported
by the enterprise repo as a Go module dependency.

Introduces pkg/cpextension (shared Extension interface + ServerContext) and
pkg/cpserver (Run() entrypoint with functional options) so the enterprise
main.go can call cpserver.Run(cpserver.WithExtensions(...)) without duplicating
the 20-step server bootstrap. Adds db/migrations/embed.go for go:embed access
to OSS SQL migrations from the enterprise module.

cmd/control-plane/main.go is reduced to a 10-line wrapper around cpserver.Run.

envd/main.go

@@ -50,7 +50,7 @@ const (
 )
 
 var (
-	Version = "0.5.4"
+	Version = "0.1.0"
 
 	commitSHA string
 
@@ -197,7 +197,7 @@ func main() {
 	portSubsystem.Start(ctx)
 	defer portSubsystem.Stop()
 
-	service := api.New(&envLogger, defaults, mmdsChan, isNotFC, ctx, portSubsystem)
+	service := api.New(&envLogger, defaults, mmdsChan, isNotFC, ctx, portSubsystem, Version)
 	handler := api.HandlerFromMux(service, m)
 	middleware := authn.NewMiddleware(permissions.AuthenticateUsername)