fix solver- vybiti do site pred zapornym nakupem

backend/tests/test_planning_dispatch_milp.py

@@ -208,7 +208,7 @@ class PlanningDispatchMilpTests(unittest.TestCase):
         self.assertGreaterEqual(results[0].grid_setpoint_w, 0)
 
     def test_export_implies_end_soc_at_least_reserve(self) -> None:
-        """Při ge >= 1 W musí koncové soc[t] >= arb_base_wh (rezerva z DB)."""
+        """Bez arbitrážní relaxace: při ge >= 1 W musí koncové soc[t] >= arb_base_wh (rezerva z DB)."""
         slots = [
             _slot(load=500, buy=2.0, sell=8.0, pv_a=0, pv_b=0),
             _slot(load=500, buy=2.0, sell=8.0, pv_a=0, pv_b=0),
@@ -254,6 +254,82 @@ class PlanningDispatchMilpTests(unittest.TestCase):
                     msg="export slot must end at or above reserve SoC",
                 )
 
+    def test_export_before_extreme_negative_buy_can_end_below_reserve(self) -> None:
+        """
+        Při relaxovaném soc_min (záporný buy v lookahead) smí významný export skončit u planner floor,
+        ne u provozní rezervy — jinak nejde ráno vypustit do sítě a nachystat kapacitu před levným nákupem.
+        """
+        base = datetime(2026, 4, 3, 6, 0, tzinfo=timezone.utc)
+        s0 = PlanningSlot(
+            interval_start=base,
+            buy_price=2.5,
+            sell_price=2.0,
+            pv_a_forecast_w=0,
+            pv_b_forecast_w=0,
+            load_baseline_w=400,
+            ev1_connected=False,
+            ev2_connected=False,
+            is_predicted_price=False,
+            allow_charge=True,
+            allow_discharge_export=True,
+        )
+        s1 = PlanningSlot(
+            interval_start=base + timedelta(minutes=15),
+            buy_price=-12.0,
+            sell_price=-0.5,
+            pv_a_forecast_w=0,
+            pv_b_forecast_w=0,
+            load_baseline_w=400,
+            ev1_connected=False,
+            ev2_connected=False,
+            is_predicted_price=False,
+            allow_charge=True,
+            allow_discharge_export=True,
+        )
+        slots = [s0, s1]
+        battery = _battery(uc_wh=10_000.0, min_pct=10.0, arb_pct=20.0)
+        battery.planner_extreme_buy_threshold_czk_kwh = -2.0
+        battery.planner_discharge_floor_percent = 5.0
+        battery.max_charge_power_w = 50_000
+        battery.max_discharge_power_w = 50_000
+        hp = SimpleNamespace(
+            rated_heating_power_w=0,
+            tuv_min_temp_c=45.0,
+            tuv_target_temp_c=55.0,
+        )
+        grid = SimpleNamespace(max_import_power_w=50_000, max_export_power_w=50_000)
+        vehicles = [
+            SimpleNamespace(
+                max_charge_power_w=0,
+                battery_capacity_kwh=1.0,
+                default_target_soc_pct=80.0,
+            ),
+            SimpleNamespace(
+                max_charge_power_w=0,
+                battery_capacity_kwh=1.0,
+                default_target_soc_pct=80.0,
+            ),
+        ]
+        soc0 = 0.88 * battery.usable_capacity_wh
+        results, _ms = solve_dispatch(
+            slots,
+            battery,
+            hp,
+            grid,
+            [None, None],
+            vehicles,
+            soc0,
+            50.0,
+            tuv_delta_stats=None,
+            operating_mode="AUTO",
+        )
+        self.assertEqual(len(results), 2)
+        if results[0].grid_setpoint_w < 0:
+            self.assertLess(
+                results[0].battery_soc_target,
+                19.0,
+                msg="with relaxed soc_min, first-slot export should be able to finish below reserve %",
+            )
 
     def test_grid_import_soft_cap_penalizes_breaker_overdraw(self) -> None:
         """