fix(compare): date report cards with their own inspection date, never the legacy one

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

backend/models.py

@@ -156,6 +156,9 @@ class FactOfstedInspection(Base):
     rc_leadership_governance = Column(Integer)
     rc_early_years = Column(Integer)
     rc_sixth_form = Column(Integer)
+    # Start date of the report-card inspection itself (renewed framework,
+    # Nov 2025+). Null for rows without report-card grades.
+    rc_inspection_date = Column(Date)
     report_url = Column(Text)