chore: Remove vue-multiselect and migrate to next components (#13506)

# Pull Request Template

## Description

This PR includes:
1. Removes multiselect usage from the Merge Contact modal (Conversation
sidebar) and replaces it with the existing component used on the Contact
Details page.
2. Replaces legacy form and multiselect elements in Add and Edit
automations flows with next components.**(Also check Macros)**
3. Replace multiselect with ComboBox in contact form country field.
4. Replace multiselect with TagInput in create/edit attribute form.
5. Replace multiselect with TagInput for agent selection in inbox
creation.
6. Replace multiselect with ComboBox in Facebook channel page selection

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

**Screenshots**

1. **Merge modal**
<img width="741" height="449" alt="image"
src="https://github.com/user-attachments/assets/a05a96ec-0692-4d94-9e27-d3e85fd143e4"
/>
<img width="741" height="449" alt="image"
src="https://github.com/user-attachments/assets/fc1dc977-689d-4440-869d-2124e4ca9083"
/>

2. **Automations**
<img width="849" height="1089" alt="image"
src="https://github.com/user-attachments/assets/b0155f06-ab21-4f90-a2c8-5bfbd97b08f7"
/>
<img width="813" height="879" alt="image"
src="https://github.com/user-attachments/assets/0921ac4a-88f5-49ac-a776-cc02941b479c"
/>
<img width="849" height="826" alt="image"
src="https://github.com/user-attachments/assets/44358dae-a076-4e10-b7ba-a4e40ccd817f"
/>

3. **Country field**
<img width="462" height="483" alt="image"
src="https://github.com/user-attachments/assets/d5db9aa1-b859-4327-9960-957d7091678f"
/>

4. **Add/Edit attribute form**
<img width="619" height="646" alt="image"
src="https://github.com/user-attachments/assets/6ab2ea94-73e5-40b8-ac29-399c0543fa7b"
/>
<img width="619" height="646" alt="image"
src="https://github.com/user-attachments/assets/b4c5bb0e-baa0-4ef7-a6a2-adb0f0203243"
/>
<img width="635" height="731" alt="image"
src="https://github.com/user-attachments/assets/74890c80-b213-4567-bf5f-4789dda39d2d"
/>

5. **Agent selection in inbox creation**
<img width="635" height="534" alt="image"
src="https://github.com/user-attachments/assets/0003bad1-1a75-4f20-b014-587e1c19a620"
/>
<img width="809" height="602" alt="image"
src="https://github.com/user-attachments/assets/5e7ab635-7340-420a-a191-e6cd49c02704"
/>

7. **Facebook channel page selection**
<img width="597" height="444" alt="image"
src="https://github.com/user-attachments/assets/f7ec8d84-0a7d-4bc6-92a1-a1365178e319"
/>
<img width="597" height="444" alt="image"
src="https://github.com/user-attachments/assets/d0596c4d-94c1-4544-8b50-e7103ff207a6"
/>
<img width="597" height="444" alt="image"
src="https://github.com/user-attachments/assets/be097921-011b-4dbe-b5f1-5d1306e25349"
/>



## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

app/javascript/dashboard/components-next/dialog/Dialog.vue

@@ -53,6 +53,11 @@ const props = defineProps({
     default: 'lg',
     validator: value => ['3xl', '2xl', 'xl', 'lg', 'md', 'sm'].includes(value),
   },
+  position: {
+    type: String,
+    default: 'center',
+    validator: value => ['center', 'top'].includes(value),
+  },
 });
 
 const emit = defineEmits(['confirm', 'close']);
@@ -61,6 +66,7 @@ const { t } = useI18n();
 
 const dialogRef = ref(null);
 const dialogContentRef = ref(null);
+const isOpen = ref(false);
 
 const maxWidthClass = computed(() => {
   const classesMap = {
@@ -75,13 +81,19 @@ const maxWidthClass = computed(() => {
   return classesMap[props.width] ?? 'max-w-md';
 });
 
+const positionClass = computed(() =>
+  props.position === 'top' ? 'dialog-position-top' : ''
+);
+
 const open = () => {
+  isOpen.value = true;
   dialogRef.value?.showModal();
 };
 
 const close = () => {
   emit('close');
   dialogRef.value?.close();
+  isOpen.value = false;
 };
 
 const confirm = () => {
@@ -98,6 +110,7 @@ defineExpose({ open, close });
       class="w-full transition-all duration-300 ease-in-out shadow-xl rounded-xl"
       :class="[
         maxWidthClass,
+        positionClass,
         overflowYAuto ? 'overflow-y-auto' : 'overflow-visible',
       ]"
       @close="close"
@@ -105,7 +118,7 @@ defineExpose({ open, close });
       <OnClickOutside @trigger="close">
         <form
           ref="dialogContentRef"
-          class="flex flex-col w-full h-auto gap-6 p-6 overflow-visible text-left align-middle transition-all duration-300 ease-in-out transform bg-n-alpha-3 backdrop-blur-[100px] shadow-xl rounded-xl"
+          class="flex flex-col w-full h-auto gap-6 p-6 overflow-visible text-start align-middle transition-all duration-300 ease-in-out transform bg-n-alpha-3 backdrop-blur-[100px] shadow-xl rounded-xl"
           @submit.prevent="confirm"
           @click.stop
         >
@@ -119,7 +132,7 @@ defineExpose({ open, close });
               </p>
             </slot>
           </div>
-          <slot />
+          <slot v-if="isOpen" />
           <!-- Dialog content will be injected here -->
           <slot name="footer">
             <div
@@ -156,4 +169,9 @@ defineExpose({ open, close });
 dialog::backdrop {
   @apply bg-n-alpha-black1 backdrop-blur-[4px];
 }
+
+.dialog-position-top {
+  margin-top: clamp(2rem, 5vh, 5rem);
+  margin-bottom: auto;
+}
 </style>