feat: Art. 26 Joint Controller + DSFA checklists for Social Media sections

New checklists:
- JOINT_CONTROLLER_CHECKLIST (Art. 26 DSGVO, 7 checks):
  Joint parties, arrangement, contact point, processing split,
  data categories, third-country transfer (USA), rights
- DSFA_CHECKLIST (Art. 35 DSGVO, 5 checks):
  Description, necessity, risk assessment, measures, DSB involvement

Section detection: 'Datenschutzerklaerung fuer Social Media' → social_media,
'Datenschutzfolgeabschaetzung/Risikoanalyse' → dsfa

classify_document_type: DSFA and social_media detected before generic DSE

Frontend: DOC_TYPES dropdown + ChecklistView labels updated

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

admin-compliance/app/sdk/agent/_components/DocCheckTab.tsx

@@ -12,6 +12,8 @@ interface DocEntry {
 
 const DOC_TYPES = [
   { id: 'dse', label: 'DSI (Datenschutzinformation)' },
+  { id: 'social_media', label: 'DSE Social Media (Art. 26)' },
+  { id: 'dsfa', label: 'DSFA (Art. 35)' },
   { id: 'agb', label: 'AGB / Nutzungsbedingungen' },
   { id: 'impressum', label: 'Impressum' },
   { id: 'cookie', label: 'Cookie-Richtlinie' },