fix(cra): prod hang-guard /readiness machinery + robuster Datenblatt-JSON-Parse

#1 _machinery_obligations: SET statement_timeout=4s + run_in_threadpool — auf
   prod hing die maschinen-Query ~30s (langsame/unindizierte DB nach DB-Swap)
   und blockierte den async-Worker. Jetzt: bei Langsamkeit graceful 'keine
   Maschinen-Pflichten' statt Hang. (Fehlender prod-Index = Controls/DB-Session.)
#2 parse_grenzen_json: tolerant ggue. ```json-Fences / Prosa-umschlossenem JSON
   (gehostete Modelle wie OVH ignorieren z.T. response_format) → Datenblatt-
   Extraktion liefert auch ueber den OVH-Fallback Felder.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend-compliance/compliance/services/cra_datasheet_extractor.py

@@ -91,11 +91,33 @@ def _system_prompt() -> str:
     )
 
 
+def _coerce_json(raw: str):
+    """Tolerant JSON load: handle ```json fences / surrounding prose (some hosted
+    models, e.g. OVH, ignore response_format and wrap the object)."""
+    s = (raw or "").strip()
+    try:
+        return json.loads(s)
+    except (json.JSONDecodeError, TypeError):
+        pass
+    if "```" in s:
+        parts = s.split("```")
+        if len(parts) > 1:
+            s = parts[1].lstrip()
+            if s[:4].lower() == "json":
+                s = s[4:]
+    i, j = s.find("{"), s.rfind("}")
+    if i != -1 and j > i:
+        try:
+            return json.loads(s[i:j + 1])
+        except (json.JSONDecodeError, TypeError):
+            return None
+    return None
+
+
 def parse_grenzen_json(raw: str) -> dict:
     """Parse the LLM response into {key: {value, source}} for known keys only."""
-    try:
-        data = json.loads(raw)
-    except (json.JSONDecodeError, TypeError):
+    data = _coerce_json(raw)
+    if not isinstance(data, dict):
         return {}
     fields = data.get("fields") if isinstance(data, dict) else None
     if not isinstance(fields, dict):