fix: replace Presentation type annotation with Any in pptx_parser

Method signature 'def _extract_metadata(self, prs: Presentation)' references
Presentation at class-definition time (evaluated on import), causing NameError
since Presentation is no longer imported at module level. Replace with Any.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

semantica/parse/pptx_parser.py

@@ -225,7 +225,7 @@ class PPTXParser:
             images=images,
         )
 
-    def _extract_metadata(self, prs: Presentation) -> Dict[str, Any]:
+    def _extract_metadata(self, prs: Any) -> Dict[str, Any]:
         """Extract presentation metadata."""
         metadata = {}