fix(entrypoint): make /data traversable; hostname gate first (v1.0.0)

Go TempDir bind mounts arrive as 0700; after chown panel:panel, OpenDKIM
could not reach KeyTable and the container crash-looped. chmod 755 /data,
check SELFPOST_HOSTNAME before /data setup, and harden the e2e stand
(restart: no, readiness logs).

Co-Authored-By: Composer <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

test/e2e/compose.override.yml

@@ -16,6 +16,10 @@
 
 services:
   selfpost:
+    # Crash-looping with unless-stopped makes `compose exec` fail with
+    # "Container is restarting" and hides the entrypoint/supervisord exit
+    # reason; keep the stand exited so logs stay attached to one attempt.
+    restart: "no"
     build:
       # Resolved relative to --project-directory (.stage), NOT this file's own
       # directory — compose build.context paths follow the project directory,