rework: address review feedback on PR #126

Changes per sneak's review:
- Delete docker-compose.yml, add example stanza to README
- Define custom domain types: ImageID, ContainerID, UnparsedURL
- Use custom types in all function signatures throughout codebase
- Restore imageID parameter (as domain.ImageID) in deploy pipeline
- buildContainerOptions now takes ImageID directly instead of
  constructing image tag from deploymentID
- Fix pre-existing JS formatting (prettier)

make check passes with zero failures.

internal/service/deploy/export_test.go

@@ -10,6 +10,7 @@ import (
 
 	"git.eeqj.de/sneak/upaas/internal/config"
 	"git.eeqj.de/sneak/upaas/internal/docker"
+	"git.eeqj.de/sneak/upaas/internal/domain"
 	"git.eeqj.de/sneak/upaas/internal/models"
 )
 
@@ -86,7 +87,7 @@ func (svc *Service) GetBuildDirExported(appName string) string {
 func (svc *Service) BuildContainerOptionsExported(
 	ctx context.Context,
 	app *models.App,
-	imageID string,
+	imageID domain.ImageID,
 ) (docker.CreateContainerOptions, error) {
 	return svc.buildContainerOptions(ctx, app, imageID)
 }