Add Gitea registry support and fix cross-device archiving

- Update docker-compose.yml to reference Gitea registry image
- Add docker-publish.cmd for building and pushing to Gitea
- Fix ArchiveService to handle cross-device moves by falling back
  to copy+delete when input and archive are on different volumes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -1,5 +1,6 @@
 services:
   discord-archive:
+    image: git.thecozycat.net/aj/discordarchivemanager:latest
     build: .
     volumes:
       - ./input:/app/input