fix(tiktok): Resolve media upload failures and gate attachments by conversation capability (#13643)

This PR fixes TikTok attachment send failures and adds a
capability-based guard so attachments are only enabled for conversations
that support media sending.

- Fixed TikTok media upload request formatting so TikTok accepts image
uploads reliably.
- Added TikTok capability check (IMAGE_SEND) during conversation
creation.
- Stored capability in
conversation.additional_attributes.tiktok_capabilities.
- Updated reply composer UI to disable/hide attachment upload for TikTok
conversations where image_send is false.

Fixes
https://linear.app/chatwoot/issue/CW-6532/enable-attachments-based-on-the-conversation-capability
and
https://linear.app/chatwoot/issue/CW-6996/unable-to-send-image-attachments-to-tiktok-customer-400-parsing-error

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>

app/javascript/dashboard/components/widgets/conversation/ReplyBox.vue

@@ -273,6 +273,10 @@ export default {
       return MESSAGE_MAX_LENGTH.GENERAL;
     },
     showFileUpload() {
+      const { image_send: imageSend } =
+        this.currentChat?.additional_attributes?.tiktok_capabilities ?? {};
+      const tiktokAttachmentSupported = imageSend ?? true;
+
       return (
         this.isAWebWidgetInbox ||
         this.isAFacebookInbox ||
@@ -283,7 +287,7 @@ export default {
         this.isATelegramChannel ||
         this.isALineChannel ||
         this.isAnInstagramChannel ||
-        this.isATiktokChannel
+        (this.isATiktokChannel && tiktokAttachmentSupported)
       );
     },
     replyButtonLabel() {
@@ -706,6 +710,7 @@ export default {
 
       // Don't handle paste if editor is disabled
       if (this.isEditorDisabled) return;
+      if (!this.showFileUpload && !this.isOnPrivateNote) return;
 
       // Filter valid files (non-zero size)
       Array.from(e.clipboardData.files)
@@ -1025,6 +1030,8 @@ export default {
       });
     },
     attachFile({ blob, file }) {
+      if (!this.showFileUpload && !this.isOnPrivateNote) return;
+
       const reader = new FileReader();
       reader.readAsDataURL(file.file);
       reader.onloadend = () => {