[nudostarforum] add support (#8664)

Add support for nudostar.com forum (XenForo-based forum site).
This is separate from the existing nudostar.py which handles nudostar.tv.

Supports:
- Thread extraction with pagination
- Individual post extraction
- Authentication via xf_user cookie or username/password
- Internal attachments (both linked and embedded images)
- External image host URLs (queued for recursive processing)

gallery_dl/extractor/__init__.py

@@ -146,6 +146,7 @@ modules = [
     "nozomi",
     "nsfwalbum",
     "nudostar",
+    "nudostarforum",
     "okporn",
     "paheal",
     "patreon",