fix(whatsapp): refresh inboxes when opening new conversation composer (#15337)

When an agent starts a new conversation, the WhatsApp template picker in
the composer only shows templates that were already loaded into the
frontend store — it doesn't refresh when the composer opens. If a
template sync completed after the store was last populated, the newly
synced template shows up on the inbox's Settings > Templates page (which
always refetches on load) but not in the New Conversation composer,
since that view relied solely on the account-cache-invalidated websocket
event, which doesn't always reach an already-open session in time.

## What changed
- `ComposeConversation.vue` now dispatches a cache-aware `inboxes/get`
refetch every time the composer popover opens, so the WhatsApp template
list is current before an agent picks a template to message a customer.
The refetch checks the account's cache key first and only re-pulls the
full inbox list when it's actually stale, so it stays cheap in the
common case.

## How to reproduce
1. Sync/update WhatsApp templates for an inbox (e.g. via Settings >
Inboxes > [WhatsApp inbox] > Sync Templates).
2. Without reloading the page, open the New Conversation composer for
that inbox and check the WhatsApp template picker — a newly synced
template may be missing until this fix.

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

spec/services/whatsapp/providers/whatsapp_cloud_service_spec.rb

@@ -383,13 +383,23 @@ describe Whatsapp::Providers::WhatsappCloudService do
           )
 
         timstamp = whatsapp_channel.reload.message_templates_last_updated
-        expect(subject.sync_templates).to be(true)
+        expect(whatsapp_channel.account).to receive(:update_cache_key).with('inbox').and_call_original
+        subject.sync_templates
         expect(whatsapp_channel.reload.message_templates.first).to eq({ id: '123456789', name: 'test_template' }.stringify_keys)
         expect(whatsapp_channel.reload.message_templates.second).to eq({ id: '123456789', name: 'next_template' }.stringify_keys)
         expect(whatsapp_channel.reload.message_templates.last).to eq({ id: '123456789', name: 'last_template' }.stringify_keys)
         expect(whatsapp_channel.reload.message_templates_last_updated).not_to eq(timstamp)
       end
 
+      it 'does not bump the inbox cache key when no templates are returned' do
+        stub_request(:get, 'https://graph.facebook.com/v14.0/123456789/message_templates')
+          .with(headers: { 'Authorization' => 'Bearer test_key' })
+          .to_return(status: 200, headers: response_headers, body: { data: [] }.to_json)
+
+        expect(whatsapp_channel.account).not_to receive(:update_cache_key)
+        subject.sync_templates
+      end
+
       it 'updates message_templates_last_updated even when template request fails' do
         stub_request(:get, 'https://graph.facebook.com/v14.0/123456789/message_templates')
           .with(headers: { 'Authorization' => 'Bearer test_key' })