feat: Fix DSFA dedup + expand all checklists to 56 total checks

Fixes:
- 'Risikoabwaegung' is sub-section of DSFA → added to SKIP_HEADINGS
- 'Social Media' standalone heading → recognized as social_media DSE
- Removed 'risikobew' from DSFA pattern (was too broad)

Expanded checklists:
- Widerruf: 4→7 checks (+Empfaenger, kein Grund, §312k Button)
- AGB: 4→9 checks (+Zahlung, Lieferung, Gewaehrleistung, Kuendigung, Datenschutz)
- Social Media: +1 (Social Bookmarks)
- DSFA: +1 (LFDI Richtlinie)

Total: 47→56 Regex-Checks across 7 document types:
DSI=9, Cookie=5, Social Media=10, DSFA=8, Impressum=6, Widerruf=7, AGB=9

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/api/agent_doc_check_routes.py

@@ -264,7 +264,8 @@ SECTION_TYPE_MAP = [
     (r"^impressum$", "impressum"),
     (r"^(?:agb|allgemeine geschäftsbedingungen|nutzungsbedingungen)$", "agb"),
     # DSFA MUST be checked BEFORE social_media (both can contain "Social Media")
-    (r"datenschutzfolge|dsfa|risikoanalyse|risikobew(?:ae|ä)gung", "dsfa"),
+    (r"datenschutzfolge|dsfa|risikoanalyse", "dsfa"),
+    (r"^social\s*media$", "social_media"),  # Standalone heading "Social Media" = DSE
     (r"datenschutzerkl(?:ae|ä)rung.*social|datenschutz\s+f(?:ue|ü)r\s+social", "social_media"),
 ]
 
@@ -326,10 +327,21 @@ def _split_into_sections(text: str, parent_label: str, url: str) -> list[dict]:
     return sections
 
 
+# Headings to skip — sub-sections of other documents, not standalone
+SKIP_HEADINGS = {
+    "nutzungskonzept social media",  # Internal concept, no legal checklist
+    "risikoabwägung und datenschutzfolgenabschätzung",  # Sub-section of DSFA
+    "risikoabwaegung und datenschutzfolgenabschaetzung",
+}
+
+
 def _classify_section(heading: str) -> str | None:
     """Classify a section heading into a document type."""
     import re as _re
-    heading_lower = heading.lower()
+    heading_lower = heading.lower().strip()
+    # Skip known sub-sections
+    if heading_lower in SKIP_HEADINGS:
+        return None
     for pattern, doc_type in SECTION_TYPE_MAP:
         if _re.search(pattern, heading_lower):
             return doc_type