Implement proactive forecast-driven car charging strategy

- Replace reactive export-threshold wallbox activation with proactive
  logic: WallboxA/B activate when forecast ≥ mid AND PV ≥ threshold
  AND SOC ≥ 35%, without requiring grid export surplus
- Add WallboxB no-car detection via grid-delta probe (no PM available):
  after probe window, if grid shift < GridDeltaThreshW → no car, retry
  after configured timeout
- Add EOD soft stop: after 16:00, stop proactive car charging if
  remaining PV estimate can't cover battery deficit to 90% by sunset
- WW boost no longer requires export threshold; dynamic setpoint uses
  tank top temp + hysteresis + boost delta, capped at 60°C
- Proactive wallboxes bypass import-hysteresis shutdown; SOC emergency
  brake uses SOCFloor (5%) instead of standard AllConsumers gate
- Add WWTopTempC to SystemState (ww_top_temp metric from DHW cylinder)
- Add BatteryConfig (capacity_kwh), CarChargingConfig to config
- Add WWMaxSetpointC, WWHysteresisC to StrategicConfig
- Update Decide() signature: forecastKWh + sunsetTime parameters
- Update all tests; add proactive charging test cases

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/collector/collector.go

@@ -26,6 +26,7 @@ type SystemState struct {
 	PhaseL1PowerW    float64 // per-phase grid power L1 (positive=import, negative=export)
 	PhaseL2PowerW    float64 // per-phase grid power L2
 	PhaseL3PowerW    float64 // per-phase grid power L3
+	WWTopTempC       float64 // DHW cylinder top temperature (°C)
 }
 
 // IsExporting returns true if the system is exporting to grid.
@@ -91,6 +92,7 @@ func (c *Collector) Collect(ctx context.Context) (SystemState, error) {
 		{"phase_l1_power", &state.PhaseL1PowerW, 1},
 		{"phase_l2_power", &state.PhaseL2PowerW, 1},
 		{"phase_l3_power", &state.PhaseL3PowerW, 1},
+		{"ww_top_temp", &state.WWTopTempC, 1},
 	}
 
 	for _, t := range targets {
@@ -120,6 +122,7 @@ func (c *Collector) Collect(ctx context.Context) (SystemState, error) {
 		"l1_w", state.PhaseL1PowerW,
 		"l2_w", state.PhaseL2PowerW,
 		"l3_w", state.PhaseL3PowerW,
+		"ww_top_c", state.WWTopTempC,
 	)
 
 	return state, nil