fix(devices): zero out unassigned bell outputs when saving Bell Mechanisms

relay.set_config is a partial update on the firmware side — any bell
index not present in the durations/outputs maps is left completely
untouched. EditBellOutputsModal and OnboardDevice's bell config step
both only sent entries for the currently-active bell count, so
deselecting a bell (lowering the active count) never actually
deactivated its output on the device — it stayed wired to whatever it
was last set to. The only way to disable a bell was to reselect it and
explicitly set it to "Disabled", which isn't obvious.

Both now send all maxOutputs slots on every save, forcing output to 0
for anything beyond the active count, so lowering the active bell
count reaches the firmware the way it visually appears to in the UI.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/modals/bellcloud/devices/EditBellOutputsModal.jsx

@@ -51,11 +51,19 @@ export default function EditBellOutputsModal({ open, onClose, onSaved, attr, sub
       // Push to the device first — relay.set_config takes both maps in one call.
       // Only write to Firestore once the device confirms it actually applied
       // and persisted the change (sendMqttCommand's toast reports the outcome).
+      //
+      // relay.set_config is a partial update — any bell index NOT present in
+      // these maps is left untouched by the firmware. So every slot beyond
+      // activeBells must be sent explicitly as output 0 (disabled), or a bell
+      // that was previously active stays wired to its old output forever,
+      // even though it's no longer shown as active here. The only way to
+      // deactivate a bell today is to select it and set it to Disabled — this
+      // makes "deselect it" do the same thing implicitly.
       const durations = {}
       const outputs = {}
-      activeRows.forEach((r, i) => {
+      rows.forEach((r, i) => {
         durations[i] = r.timing
-        outputs[i] = r.output
+        outputs[i] = i < activeBells ? r.output : 0
       })
       await sendMqttCommand('relay.set_config', { durations, outputs })
 

frontend/src/pages/bellcloud/devices/OnboardDevice.jsx

@@ -1275,9 +1275,13 @@ function ConfigureStep({ device, onDeviceUpdated, onNext, onBack }) {
   // ── Build the command sequence + Firestore patch for each group ─────────
   const buildGroups = useCallback(() => {
     const activeBellRows = bell.rows.slice(0, bell.activeBells)
+    // relay.set_config is a partial update — any bell index NOT present in
+    // these maps is left untouched by the firmware. Send every row (not just
+    // the active ones) so anything beyond activeBells is explicitly zeroed —
+    // same fix as EditBellOutputsModal.
     const durations = {}
     const outputs = {}
-    activeBellRows.forEach((r, i) => { durations[i] = r.timing; outputs[i] = r.output })
+    bell.rows.forEach((r, i) => { durations[i] = r.timing; outputs[i] = i < bell.activeBells ? r.output : 0 })
 
     return [
       {