Fix updater GetUserByName error, mask backup credentials, clean up old scripts

- Migrate deprecated updateRepo value (Sucukdeluxe/) to new default (Administrator/)
- Mask sensitive fields (tokens, passwords) in backup export with ***
- Preserve current credentials when importing backup with masked values
- Remove 22 obsolete release_v*.mjs scripts, release_codeberg.mjs, set_version_node.mjs
- Remove release:codeberg script from package.json

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -17,7 +17,6 @@
     "test": "vitest run",
     "self-check": "tsx tests/self-check.ts",
     "release:win": "npm run build && electron-builder --publish never --win nsis portable",
-    "release:codeberg": "node scripts/release_codeberg.mjs",
     "release:gitea": "node scripts/release_gitea.mjs",
     "release:forgejo": "node scripts/release_gitea.mjs"
   },