chore: publish plugins to self-hosted Gitea

Add publish:gitea wrapper that sets USER_CONTENT_BASE to Gitea raw URLs,
and resolve the lockfile's npmmirror tarballs from registry.npmjs.org.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -24,7 +24,8 @@
     "format:check": "prettier --check \"./**/*.{js,ts}\"",
     "check:sites": "node scripts/check-plugin-sites.js",
     "check:plugin": "node scripts/live-check-plugin.js",
-    "prepare": "husky"
+    "prepare": "husky",
+    "publish:gitea": "./scripts/publish-gitea.sh"
   },
   "author": "LNReader",
   "license": "MIT",