Merge pull request 'fix(sf-legacy): velocity=0 → '—' в MarketTab (consistency со «Срок продаж»)' (#362) from fix/legacy-market-velocity-zero-as-null into main

Reviewed-on: #362

frontend/src/components/site-finder/MarketTab.tsx

@@ -60,7 +60,12 @@ export function MarketTab({ data }: Props) {
   // competitors count as proxy for active (строящихся) count for now.
   const activeCount = data.competitors.length;
   const radiusKm = getRadiusKm(data);
-  const velocityPerMonth = data.velocity?.monthly_velocity_sqm ?? null;
+  // Treat zero velocity as "no data" — backend returns 0 when competitors
+  // are unmapped to Objective ground truth (OBJ-3). Showing "0.0 м²/мес"
+  // is misleading; "—" makes it clear data is unavailable.
+  const velocityRaw = data.velocity?.monthly_velocity_sqm;
+  const velocityPerMonth =
+    velocityRaw != null && velocityRaw > 0 ? velocityRaw : null;
   const maxMixPct = getMaxMixPct(data);
   const salesPeriodMonths = getSalesPeriodMonths(data);