fix: Raise full_text limit 10K→50K + combine all DSI texts for checks

Two fixes:
1. consent-tester: full_text truncation raised from 10,000 to 50,000 chars
   (IHK Internetangebot has ~50K chars, Beschwerderecht was after 10K cutoff)
2. Backend: dse_text now combines Playwright HTML + ALL DSI discovery texts
   for mandatory content checking. Previously only used first 8K chars from
   one source, missing Verantwortlicher/DSB that were in DSI documents.

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

consent-tester/main.py

@@ -312,7 +312,7 @@ async def dsi_discovery(req: DSIDiscoveryRequest):
                 doc_type=d.doc_type,
                 word_count=d.word_count,
                 text_preview=d.text[:500] if d.text else "",
-                full_text=d.text[:10000] if d.text else "",
+                full_text=d.text[:50000] if d.text else "",
             )
             for d in result.documents
         ],