Fix cache loading with Report.from_dict() method

The Report.to_dict() serializes range as {from, to} but constructor
expects range_from/range_to. Added from_dict() classmethod to properly
deserialize cached data, reconstructing all nested objects (Engagement,
Comment, SubScores, RedditItem, XItem).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/last30days.py

@@ -211,7 +211,7 @@ def main():
         cached = cache.load_cache(cache_key)
         if cached:
             # Use cached data
-            report = schema.Report(**cached)
+            report = schema.Report.from_dict(cached)
             output_result(report, args.emit)
             return