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/store/modules/appConfig.js

@@ -21,6 +21,13 @@ const state = {
   widgetStyle: 'standard',
   darkMode: 'light',
   isUpdatingRoute: false,
+  welcomeTitle: '',
+  welcomeDescription: '',
+  availableMessage: '',
+  unavailableMessage: '',
+  enableFileUpload: true,
+  enableEmojiPicker: true,
+  enableEndConversation: true,
 };
 
 export const getters = {
@@ -34,6 +41,13 @@ export const getters = {
   darkMode: $state => $state.darkMode,
   getShowUnreadMessagesDialog: $state => $state.showUnreadMessagesDialog,
   getIsUpdatingRoute: _state => _state.isUpdatingRoute,
+  getWelcomeHeading: $state => $state.welcomeTitle,
+  getWelcomeTagline: $state => $state.welcomeDescription,
+  getAvailableMessage: $state => $state.availableMessage,
+  getUnavailableMessage: $state => $state.unavailableMessage,
+  getShouldShowFilePicker: $state => $state.enableFileUpload,
+  getShouldShowEmojiPicker: $state => $state.enableEmojiPicker,
+  getCanUserEndConversation: $state => $state.enableEndConversation,
 };
 
 export const actions = {
@@ -46,6 +60,13 @@ export const actions = {
       showUnreadMessagesDialog,
       widgetStyle = 'rounded',
       darkMode = 'light',
+      welcomeTitle = '',
+      welcomeDescription = '',
+      availableMessage = '',
+      unavailableMessage = '',
+      enableFileUpload = true,
+      enableEmojiPicker = true,
+      enableEndConversation = true,
     }
   ) {
     commit(SET_WIDGET_APP_CONFIG, {
@@ -55,6 +76,13 @@ export const actions = {
       showUnreadMessagesDialog: !!showUnreadMessagesDialog,
       widgetStyle,
       darkMode,
+      welcomeTitle,
+      welcomeDescription,
+      availableMessage,
+      unavailableMessage,
+      enableFileUpload,
+      enableEmojiPicker,
+      enableEndConversation,
     });
   },
   toggleWidgetOpen({ commit }, isWidgetOpen) {
@@ -90,6 +118,13 @@ export const mutations = {
     $state.darkMode = data.darkMode;
     $state.locale = data.locale || $state.locale;
     $state.showUnreadMessagesDialog = data.showUnreadMessagesDialog;
+    $state.welcomeTitle = data.welcomeTitle;
+    $state.welcomeDescription = data.welcomeDescription;
+    $state.availableMessage = data.availableMessage;
+    $state.unavailableMessage = data.unavailableMessage;
+    $state.enableFileUpload = data.enableFileUpload;
+    $state.enableEmojiPicker = data.enableEmojiPicker;
+    $state.enableEndConversation = data.enableEndConversation;
   },
   [TOGGLE_WIDGET_OPEN]($state, isWidgetOpen) {
     $state.isWidgetOpen = isWidgetOpen;