webapp: optimize spacing on bottom of cards

if the last child in a card (div.card > div.card-body) adds bottom
marging, we don't want the card to add more space through its
padding-bottom. most cards have children that add sufficient space
at the bottom anyways.

webapp/src/scss/styles.scss

@@ -48,3 +48,7 @@ div.accordion-item.accordion-table div.accordion-body {
 div.card.card-table div.card-body {
     padding: 0;
 }
+
+div.card div.card-body > :last-child {
+    margin-bottom: auto !important;
+}

webapp/src/views/DtuAdminView.vue

@@ -50,7 +50,7 @@
                         <BIconInfoCircle v-tooltip :title="$t('dtuadmin.CmtPaLevelHint')" />
                     </label>
                     <div class="col-sm-10">
-                        <div class="input-group mb-3">
+                        <div class="input-group">
                             <input
                                 type="range"
                                 class="form-control form-range"
@@ -91,7 +91,7 @@
                         <BIconInfoCircle v-tooltip :title="$t('dtuadmin.CmtFrequencyHint')" />
                     </label>
                     <div class="col-sm-10">
-                        <div class="input-group mb-3">
+                        <div class="input-group">
                             <input
                                 type="range"
                                 class="form-control form-range"

webapp/src/views/InverterAdminView.vue

@@ -25,8 +25,8 @@
                         {{ $t('inverteradmin.Add') }}
                     </button>
                 </div>
-                <div class="alert alert-secondary" role="alert" v-html="$t('inverteradmin.AddHint')"></div>
             </form>
+            <div class="alert alert-secondary" role="alert" v-html="$t('inverteradmin.AddHint')"></div>
         </CardElement>
 
         <CardElement :text="$t('inverteradmin.InverterList')" textVariant="text-bg-primary" add-space>