fix: prevent numeric input from resetting to zero on blur without edit (#7560)

When a numeric input field was focused but not edited, the blur handler
called toNumber(null) which returned 0 via parseFloat(null) → NaN → 0.
Now we skip emitting the update when numericTemp is null (no edits made).

dashboard/src/components/shared/ConfigItemRenderer.vue

@@ -161,7 +161,7 @@
       <v-text-field
         :model-value="numericTemp ?? modelValue"
         @update:model-value="val => (numericTemp = val)"
-        @blur="() => { emitUpdate(toNumber(numericTemp)); numericTemp = null }"
+        @blur="() => { if (numericTemp != null) { emitUpdate(toNumber(numericTemp)) } numericTemp = null }"
         density="compact"
         variant="outlined"
         class="config-field"