fix(tradein/v2): mark location coefficient as informational; clarify price-history source

- LocationDrawer/HeroBar: disclaimer that the location coefficient is illustrative
  and does not change the final quoted estimate (estimator does not use it).
- mappers.ts: comment clarifying price-history 'avito_imv'/'yandex_valuation' are
  real archived-listing discriminators, not AVM valuations (card already honest).
LOW audit R2 (#7c, #8).

tradein-mvp/frontend/src/components/trade-in/v2/LocationDrawer.tsx

@@ -358,6 +358,19 @@ export function LocationDrawer({
                 {data.resultLabel}
               </span>
             </div>
+            {/* Fix #7c (audit): the estimator never reads this coefficient — it's
+                illustrative/reference only. Without this line the ₽-vs-₽ layout
+                above reads as if it changes the quoted price. */}
+            <div
+              style={{
+                marginTop: 8,
+                fontSize: 10.5,
+                lineHeight: 1.5,
+                color: tokens.muted3,
+              }}
+            >
+              Справочно: поправка на локацию не влияет на итоговую оценку.
+            </div>
             {data.factors.length > 0 ? (
               <ul
                 style={{

tradein-mvp/frontend/src/components/trade-in/v2/mappers.ts

@@ -1616,6 +1616,9 @@ const PH_Y_SPAN = PH_Y_BOTTOM - PH_Y_TOP; // 175
 export const PH_GRID_Y = [20, 64, 108, 151, 195]; // 5 gridlines, evenly spaced (top → bottom)
 // Both polylines are drawn from these source keys; the Y zoom is computed over
 // the union of their finite medians so the two series share one axis.
+// NB: 'avito_imv'/'yandex_valuation' are scrape-origin discriminators on real
+// archived listing rows (house_placement_history), NOT AVM model valuations —
+// the card plots median ₽/m² of actual past listings. (LOW audit R2 #8, verified.)
 const PH_SERIES_SOURCES = ["avito_imv", "yandex_valuation"];
 
 export function phYearX(i: number, n: number): number {