Keep deployment logs findable after the container is recreated (closes #214)

Deployment logs were stored under a directory named after the container's hostname, and the path was worked out again from the current hostname on download. Docker gives a recreated container a new hostname, so every older log download returned 404. New logs now go to `logs/<appname>/` with no hostname in the path. Logs written by older versions under an old hostname directory are still found by looking one directory deeper, inside the same confined log root. Tests cover both the hostname-free path and downloading an old-layout log.

Model: opus-5-5

internal/service/deploy/deploy.go

@@ -261,15 +261,14 @@ func (svc *Service) GetBuildDir(appName string) string {
 
 // GetLogFilePath returns the path to the log file for a deployment.
 // Returns empty string if the path cannot be determined.
+//
+// The path must not depend on the container's hostname: Docker assigns a
+// new one whenever the container is recreated, and older logs would then
+// no longer be found.
 func (svc *Service) GetLogFilePath(
 	app *models.App,
 	deployment *models.Deployment,
 ) string {
-	hostname, err := os.Hostname()
-	if err != nil {
-		hostname = "unknown"
-	}
-
 	// Get commit SHA
 	sha := ""
 	if deployment.CommitSHA.Valid && deployment.CommitSHA.String != "" {
@@ -291,7 +290,7 @@ func (svc *Service) GetLogFilePath(
 		filename = fmt.Sprintf("%s_%s.log.txt", app.Name, timestamp)
 	}
 
-	return filepath.Join(svc.config.DataDir, "logs", hostname, app.Name, filename)
+	return filepath.Join(svc.config.DataDir, "logs", app.Name, filename)
 }
 
 // GetLogDir returns the root directory under which all deployment log
@@ -1294,7 +1293,7 @@ func (svc *Service) failDeployment(
 }
 
 // writeLogsToFile writes the deployment logs to a file on disk.
-// Structure: DataDir/logs/<hostname>/<appname>/<appname>_<sha>_<timestamp>.log.txt
+// Structure: DataDir/logs/<appname>/<appname>_<sha>_<timestamp>.log.txt
 func (svc *Service) writeLogsToFile(app *models.App, deployment *models.Deployment) {
 	if !deployment.Logs.Valid || deployment.Logs.String == "" {
 		return