add extractor registry

app/services/extractors/__init__.py

@@ -0,0 +1,25 @@
+"""Asset extractors.
+
+Each extractor exposes a single callable:
+
+    def extract(soup: BeautifulSoup, base_url: str, include_data_uris: bool) -> list[str]
+
+returning a list of absolute asset URLs for its category.
+"""
+
+from .audios import extract as extract_audios
+from .fonts import extract as extract_fonts
+from .icons_svg import extract as extract_icons
+from .images import extract as extract_images
+from .videos import extract as extract_videos
+
+# Ordered registry: key -> (group label in response, extractor callable).
+EXTRACTORS = {
+    "image": ("image", extract_images),
+    "video": ("video", extract_videos),
+    "audio": ("audio", extract_audios),
+    "svg_icon": ("svg_icon", extract_icons),
+    "font": ("font", extract_fonts),
+}
+
+__all__ = ["EXTRACTORS"]