Native DeepSeek datasheet extraction in periscope/src (Fase C3).

Pipeline and LCSC resolve call datasheet_extract; inherited extraction.py
stays in dependency as fallback. No Anthropic Console skill ids.

tests/test_purple_parts_resolver.py

@@ -452,7 +452,7 @@ async def test_lcsc_resolve_passive_success_and_cached(tmp_path, monkeypatch):
     from backend.config import settings
     from backend.periscopex.models import CapacitorSpecs, ComponentModel
     from backend.services import purple_parts
-    from backend.services import extraction as extraction_svc
+    from backend.services import datasheet_extract as extraction_svc
 
     # Billing modules are absent in the open-source repo; the endpoint under
     # test only charges when billing is enabled, so skip there.