fix(scan): TCF SQL column + cascade diagnose-logs

VW-Scan-Befunde aus 0a8aa16e:
1. TCF lookup failed 5x mit: column 'source' does not exist. Korrekt:
   'source_name' (siehe DELETE-Query in derselben Datei). Mit dem Fix
   funktioniert das TCF-Cross-Reference fuer alle Vendors statt 0.
2. Cascade tier-1 fail loggte leere message — jetzt mit type+model+base.
3. Cascade collapse (tier 2+3 unconfigured) wird beim ersten Aufruf
   geloggt damit der Operator den ENV-Mangel sofort sieht.
4. vendor_llm_extractor loggt jetzt START + 0-vendor-Return (vorher
   silent skip — sah aus als waere er nie aufgerufen worden).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/services/llm_cascade.py

@@ -119,7 +119,12 @@ async def _call_ollama(system: str, user: str,
             r.raise_for_status()
         return (r.json().get("message") or {}).get("content", "") or ""
     except Exception as e:
-        logger.warning("ollama cascade tier 1 failed: %s", e)
+        # P83-followup: explizit type+message loggen damit empty-message
+        # exceptions (z.B. ReadTimeout) diagnostizierbar sind.
+        logger.warning(
+            "ollama cascade tier 1 failed: %s (%s) model=%s base=%s",
+            str(e) or "(no message)", type(e).__name__, model, base,
+        )
         return ""
 
 
@@ -190,9 +195,21 @@ async def call_with_cascade(
     cached = _cache_get(key)
     if cached:
         cached["cached"] = True
+        logger.info("cascade cache HIT key=%s len=%d", key[-12:],
+                     len(cached.get("text", "")))
         return cached
 
     input_len = len(user)
+    # Pre-flight: warn if Tier 2 + Tier 3 are unconfigured so user knows
+    # we are de-facto running single-tier (cascade collapse).
+    if not (os.getenv("OVH_LLM_URL", "").strip()
+            and os.getenv("OVH_LLM_MODEL", "").strip()):
+        if not os.getenv("ANTHROPIC_API_KEY", "").strip():
+            logger.warning(
+                "cascade: Tier 2 (OVH) AND Tier 3 (Anthropic) unconfigured — "
+                "running on Tier 1 (Qwen) only. Set OVH_LLM_URL/MODEL/KEY "
+                "or ANTHROPIC_API_KEY to enable fallbacks."
+            )
     # Tier 1: Qwen lokal
     text = await _call_ollama(system, user, max_tokens=max_tokens)
     conf = _heuristic_confidence(text, input_len)