Add EV charging advice notification to status page

Uses hourly PV forecast data (watts per hour from forecast.solar) to
find the first contiguous block of hours where:
  PV production - base_load_w >= min_surplus_w

Shows a blue advice card on the status page:
  "Auto einstecken bis HH:MM Uhr"
  "Erwartetes Überschuss-Fenster: HH:MM – HH:MM Uhr"

Card is hidden when:
- No surplus window found (weak forecast day)
- Window has already started or passed
- A wallbox is currently active (car already charging)

Config: forecast.base_load_w (1000W), forecast.min_surplus_w (1800W)
Timestamp parsing handles both "HH:MM:SS" and "HH:MM" key formats.
Today: surplus window 11:00–13:00 (24.3 kWh forecast).

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

internal/status/status.go

@@ -136,6 +136,13 @@ type forecastView struct {
 	Quality   string
 }
 
+type chargingAdviceView struct {
+	Show         bool
+	PlugInBy     string // e.g. "11:30"
+	WindowStart  string // e.g. "12:00"
+	WindowEnd    string // e.g. "16:00"
+}
+
 type pageData struct {
 	LastUpdate       time.Time
 	ErrMsg           string
@@ -150,6 +157,7 @@ type pageData struct {
 	HasPhaseData     bool
 	Phases           []phaseView
 	Forecast         forecastView
+	ChargingAdvice   chargingAdviceView
 	Consumers        []consumerView
 }
 
@@ -253,6 +261,25 @@ func (s *Store) Handler() http.HandlerFunc {
 				Icon:      s.fcResult.QualityIcon(s.strategic),
 				Quality:   s.fcResult.Quality(s.strategic),
 			}
+
+			// Charging advice: show when surplus window is ahead and no wallbox is active
+			ws := s.fcResult.SurplusWindowStart
+			we := s.fcResult.SurplusWindowEnd
+			now := time.Now()
+			wallboxActive := s.consumers[engine.ConsumerWallboxA].active ||
+				s.consumers[engine.ConsumerWallboxB].active
+			if !ws.IsZero() && now.Before(ws) && !wallboxActive {
+				plugBy := ws.Add(-30 * time.Minute)
+				if plugBy.Before(now) {
+					plugBy = ws // less than 30 min to window — just show window start
+				}
+				data.ChargingAdvice = chargingAdviceView{
+					Show:        true,
+					PlugInBy:    plugBy.Format("15:04"),
+					WindowStart: ws.Format("15:04"),
+					WindowEnd:   we.Format("15:04"),
+				}
+			}
 		}
 		for _, c := range consumerOrder {
 			rec := s.consumers[c]
@@ -415,6 +442,33 @@ h1 { font-size: 1.4rem; font-weight: 700; color: #14532d; }
   margin-top: 0.1rem;
 }
 
+/* Charging advice card */
+.advice-card {
+  background: #eff6ff;
+  border: 1px solid #bfdbfe;
+  border-radius: 14px;
+  padding: 0.85rem 1rem;
+  margin-bottom: 1.25rem;
+}
+.advice-title {
+  font-size: 0.78rem;
+  font-weight: 700;
+  color: #1d4ed8;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  margin-bottom: 0.4rem;
+}
+.advice-main {
+  font-size: 1rem;
+  font-weight: 700;
+  color: #1e3a8a;
+}
+.advice-sub {
+  font-size: 0.78rem;
+  color: #3b82f6;
+  margin-top: 0.2rem;
+}
+
 /* Live power badge on consumers */
 .power-badge {
   font-size: 0.72rem;
@@ -583,6 +637,16 @@ h1 { font-size: 1.4rem; font-weight: 700; color: #14532d; }
 
 </div>
 
+{{if .ChargingAdvice.Show}}
+<div class="advice-card">
+  <div class="advice-title">🔌 Ladeempfehlung</div>
+  <div class="advice-main">Auto einstecken bis {{.ChargingAdvice.PlugInBy}} Uhr</div>
+  <div class="advice-sub">
+    Erwartetes Überschuss-Fenster: {{.ChargingAdvice.WindowStart}} – {{.ChargingAdvice.WindowEnd}} Uhr
+  </div>
+</div>
+{{end}}
+
 <div class="section-title">Verbraucher</div>
 
 {{range .Consumers}}