Delete preview.py

preview.py

@@ -1,7 +0,0 @@
-def safe_preview(url: str):
-    if not url:
-        return "<i>No preview available</i>"
-    blocked = ["pdf", "download"]
-    if any(b in url.lower() for b in blocked):
-        return "<i>Preview disabled (redaction-protected document)</i>"
-    return f"<iframe src='{url}' width='100%' height='400'></iframe>"