B2: tolerant JSON extraction from Claude responses + graceful fallback

_extract_json_payload handles a json/JSON/bare fence, raw JSON and JSON
embedded in prose; any unparseable response or contract violation now
degrades to the deterministic scoring_service instead of raising.
Also guards the response envelope itself (content[0].text).

B3: single home for recommendation scoring

services/recommendation_service.py holds the rules; routers/stats.py and
backend/services/stats_service.py both delegate to it. Unified rules are the
union of the two old copies: same weights/threshold, substring matching
(superset of the old exact match), tolerant key aliases, health_flags rule
kept. Endpoint response contract unchanged.

Plus: Overpass circuit breaker and concurrent zone queries in geo_service -
128 sequential calls per analysis no longer each burn a connect timeout when
the host has no outbound network.

Tests: 152 -> 194 passed.

backend/services/stats_service.py

@@ -1,12 +1,17 @@
 from __future__ import annotations
 
-from typing import Any
-
 try:
     from backend.database import db
 except ImportError:  # pragma: no cover - compatibility for direct service imports
     from database import db
 
+# Scoring rules live in services/recommendation_service.py (B3) — this module
+# only re-exports them so existing `stats_service.get_statistical_recommendation`
+# callers keep working.
+from services.recommendation_service import get_statistical_recommendation
+
+__all__ = ['summary', 'heatmap', 'get_statistical_recommendation']
+
 
 def summary() -> dict:
     return db.stats()
@@ -14,26 +19,3 @@ def summary() -> dict:
 
 def heatmap() -> list[dict]:
     return db.heatmap()
-
-
-def get_statistical_recommendation(case_data: dict[str, Any]) -> dict[str, Any]:
-    score = 0
-    age = case_data.get('age') or case_data.get('age_years')
-    elapsed = case_data.get('elapsed_hours')
-    terrain = str(case_data.get('terrain') or case_data.get('terrain_primary') or '').lower()
-    weather = str(case_data.get('weather') or case_data.get('precipitation') or '').lower()
-
-    if age is not None and age < 12:
-        score += 20
-    if elapsed is not None and elapsed >= 12:
-        score += 20
-    if any(token in terrain for token in ('лес', 'болото', 'вода')):
-        score += 15
-    if any(token in weather for token in ('дождь', 'туман', 'снег', 'ночь')):
-        score += 15
-
-    return {
-        'score': score,
-        'priority': 'high' if score >= 40 else 'normal',
-        'recommendation': 'Высокий приоритет на прочёс и дрон' if score >= 40 else 'Стандартный приоритет поиска',
-    }