feat: Support customizable welcome text, availability messages, and UI toggles (#11891)

# Pull Request Template

## Description

This PR allows users to dynamically pass custom welcome and availability
messages, along with UI feature toggles, via `window.chatwootSettings`.
If any of the following settings are provided, the widget will use them;
otherwise, it falls back to default behavior.

**New options:**
```
window.chatwootSettings = {
  welcomeTitle: 'Need help?',                        // Custom widget title
  welcomeDescription: 'We’re here to support you.',        // Subtitle in the header
  availableMessage: 'We’re online and ready to chat!', // Shown when team is online
  unavailableMessage: 'We’re currently offline.',      // Shown when team is unavailable

  enableFileUpload: true,          // Enable file attachments
  enableEmojiPicker: true,         // Enable emoji picker in chat input
  enableEndConversation: true     // Allow users to end the conversation
}
```


Fixes
https://linear.app/chatwoot/issue/CW-4589/add-options-to-windowchatwootsettings

## Type of change

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

## How Has This Been Tested?

### Loom video

https://www.loom.com/share/413fc4aa59384366b071450bd19d1bf8?sid=ff30fb4c-267c-4beb-80ab-d6f583aa960d

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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
- [ ] 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: Muhsin Keloth <muhsinkeramam@gmail.com>

app/javascript/widget/components/ChatInputWrap.vue

@@ -41,9 +41,15 @@ export default {
     ...mapGetters({
       widgetColor: 'appConfig/getWidgetColor',
       isWidgetOpen: 'appConfig/getIsWidgetOpen',
+      shouldShowFilePicker: 'appConfig/getShouldShowFilePicker',
+      shouldShowEmojiPicker: 'appConfig/getShouldShowEmojiPicker',
     }),
     showAttachment() {
-      return this.hasAttachmentsEnabled && this.userInput.length === 0;
+      return (
+        this.shouldShowFilePicker &&
+        this.hasAttachmentsEnabled &&
+        this.userInput.length === 0
+      );
     },
     showSendButton() {
       return this.userInput.length > 0;
@@ -143,7 +149,7 @@ export default {
         :on-attach="onSendAttachment"
       />
       <button
-        v-if="hasEmojiPickerEnabled"
+        v-if="shouldShowEmojiPicker && hasEmojiPickerEnabled"
         class="flex items-center justify-center min-h-8 min-w-8"
         :aria-label="$t('EMOJI.ARIA_LABEL')"
         @click="toggleEmojiPicker"
@@ -158,7 +164,7 @@ export default {
         />
       </button>
       <EmojiInput
-        v-if="showEmojiPicker"
+        v-if="shouldShowEmojiPicker && showEmojiPicker"
         v-on-clickaway="hideEmojiPicker"
         :on-click="emojiOnClick"
         @keydown.esc="hideEmojiPicker"