fix(estimator): data-age guards — sber staleness + IMV thin-market (#audit-5)

5a: _load_sber_index_series логирует warning если latest месяц серии
старее sber_index_max_age_days (дефолт 35) — расчёт не блокируется.
5b: AvitoImvSummary.thin_market (bool, дефолт False) — True когда
market_count < avito_imv_thin_market_threshold (дефолт 10). Все три
точки конструирования AvitoImvSummary обновлены. Warning при thin.

tradein-mvp/backend/app/schemas/trade_in.py

@@ -98,6 +98,10 @@ class AvitoImvSummary(BaseModel):
     lower_price: int | None = None  # нижняя граница IMV-коридора, ₽
     higher_price: int | None = None  # верхняя граница IMV-коридора, ₽
     market_count: int | None = None  # объём рынка, на котором построена оценка
+    # #audit-5b: тонкий рынок — market_count < avito_imv_thin_market_threshold.
+    # True = IMV построен на малой выборке → reliability ↓. Фронт/estimator могут
+    # использовать для понижения уверенности или отображения предупреждения.
+    thin_market: bool = False
 
 
 class DkpCorridor(BaseModel):

tradein-mvp/backend/app/services/estimator.py

@@ -1102,6 +1102,7 @@ def _load_sber_index_series(db: Session, *, region: str) -> dict[date, float]:
     """#794: monthly {period_month: index_value} for region from sber_price_index.
 
     Tries SBER_COEFF_DASHBOARDS in order; returns first non-empty series. {} on any error.
+    #audit-5a: если latest месяц серии старее sber_index_max_age_days → warning.
     """
     for dash in SBER_COEFF_DASHBOARDS:
         try:
@@ -1123,7 +1124,23 @@ def _load_sber_index_series(db: Session, *, region: str) -> dict[date, float]:
             logger.warning("sber_price_index lookup failed for %s (graceful): %s", dash, exc)
             continue
         if rows:
-            return {r["period_month"]: float(r["index_value_rub_m2"]) for r in rows}
+            series = {r["period_month"]: float(r["index_value_rub_m2"]) for r in rows}
+            # #audit-5a: data-age guard — предупреждаем о stale СберИндексе.
+            latest = max(series)
+            today = datetime.now(tz=UTC).date()
+            age_days = (today - latest).days
+            if age_days > settings.sber_index_max_age_days:
+                logger.warning(
+                    "sber_index stale #audit-5a: latest=%s age=%d days"
+                    " (> sber_index_max_age_days=%d) region=%s dash=%s"
+                    " — time-adjustment may be outdated",
+                    latest.isoformat(),
+                    age_days,
+                    settings.sber_index_max_age_days,
+                    region,
+                    dash,
+                )
+            return series
     return {}
 
 
@@ -2492,14 +2509,17 @@ async def estimate_quality(
                 int(imv_anchor["higher_price"]) if imv_anchor.get("higher_price") else None
             )
             anchor_label = "оценке Avito IMV"
+            _imv_mc = int(imv_anchor["market_count"]) if imv_anchor.get("market_count") else None
             avito_imv_summary = AvitoImvSummary(
                 recommended_price=anchor_total,
                 lower_price=(
                     int(imv_anchor["lower_price"]) if imv_anchor.get("lower_price") else None
                 ),
                 higher_price=anchor_higher,
-                market_count=(
-                    int(imv_anchor["market_count"]) if imv_anchor.get("market_count") else None
+                market_count=_imv_mc,
+                # #audit-5b: тонкий рынок — малая выборка для IMV.
+                thin_market=(
+                    _imv_mc is not None and _imv_mc < settings.avito_imv_thin_market_threshold
                 ),
             )
         elif imv_eval is not None and imv_eval.recommended_price:
@@ -2512,6 +2532,20 @@ async def estimate_quality(
                 lower_price=int(imv_eval.lower_price) if imv_eval.lower_price else None,
                 higher_price=anchor_higher,
                 market_count=imv_eval.market_count,
+                # #audit-5b: тонкий рынок — market_count < threshold.
+                thin_market=(
+                    imv_eval.market_count is not None
+                    and imv_eval.market_count < settings.avito_imv_thin_market_threshold
+                ),
+            )
+
+        # #audit-5b: thin-market warning — IMV на малой выборке → reliability ↓.
+        if avito_imv_summary is not None and avito_imv_summary.thin_market:
+            logger.warning(
+                "avito_imv thin_market #audit-5b: market_count=%s"
+                " (< avito_imv_thin_market_threshold=%d) — IMV reliability low",
+                avito_imv_summary.market_count,
+                settings.avito_imv_thin_market_threshold,
             )
 
         if anchor_total is not None:
@@ -2556,6 +2590,11 @@ async def estimate_quality(
             area=payload.area_m2,
         )
         if imv_anchor_disp is not None and imv_anchor_disp.get("recommended_price"):
+            _disp_mc = (
+                int(imv_anchor_disp["market_count"])
+                if imv_anchor_disp.get("market_count")
+                else None
+            )
             avito_imv_summary = AvitoImvSummary(
                 recommended_price=int(imv_anchor_disp["recommended_price"]),
                 lower_price=(
@@ -2568,10 +2607,10 @@ async def estimate_quality(
                     if imv_anchor_disp.get("higher_price")
                     else None
                 ),
-                market_count=(
-                    int(imv_anchor_disp["market_count"])
-                    if imv_anchor_disp.get("market_count")
-                    else None
+                market_count=_disp_mc,
+                # #audit-5b: тонкий рынок.
+                thin_market=(
+                    _disp_mc is not None and _disp_mc < settings.avito_imv_thin_market_threshold
                 ),
             )