Add configurable override duration and hard-stop thresholds

Override duration (web UI):
- Dropdown on Ein button: 30min / 1h / 2h / 4h
- Engine notified immediately via ApplyOverride() — no waiting for
  next SyncHardwareState cycle
- Aus button always uses 1h lockout (keeps consumer off for 1h)

Hard-stop thresholds that cancel active overrides:
- SOC emergency brake: now also clears ManualOverride flag so EMS
  resumes full control after the safety shutdown
- override_max_import_w (default 800W): if grid import exceeds this
  while an override is active, override is cancelled immediately
  (no hysteresis delay — protection is instant)

Config: ems.override_max_import_w (0 = disabled)

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

internal/status/status.go

@@ -534,6 +534,17 @@ h1 { font-size: 1.4rem; font-weight: 700; color: #14532d; }
 .consumer-detail.active { color: #16a34a; font-weight: 500; }
 .consumer-detail.override { color: #d97706; font-weight: 500; }
 
+.dur-select {
+  border: 1px solid #d1d5db;
+  border-radius: 8px;
+  padding: 0.3rem 0.4rem;
+  font-size: 0.75rem;
+  background: #f9fafb;
+  color: #374151;
+  cursor: pointer;
+  flex-shrink: 0;
+}
+
 .override-btn {
   border: none;
   border-radius: 8px;
@@ -673,13 +684,20 @@ h1 { font-size: 1.4rem; font-weight: 700; color: #14532d; }
   <span class="power-badge">{{formatW .LivePowerW}}</span>
   {{end}}
   {{if .CanOverride}}
-  <form method="post" action="/override">
+  <form method="post" action="/override" style="display:flex;align-items:center;gap:0.4rem;flex-shrink:0">
     <input type="hidden" name="consumer" value="{{.ConsumerKey}}">
     {{if .Active}}
     <input type="hidden" name="state" value="off">
+    <input type="hidden" name="duration" value="1h">
     <button type="submit" class="override-btn turn-off">Aus</button>
     {{else}}
     <input type="hidden" name="state" value="on">
+    <select name="duration" class="dur-select">
+      <option value="30m">30 min</option>
+      <option value="1h" selected>1 Std</option>
+      <option value="2h">2 Std</option>
+      <option value="4h">4 Std</option>
+    </select>
     <button type="submit" class="override-btn turn-on">Ein</button>
     {{end}}
   </form>