Allow direct local file upload (PDF/Image/Video) for WhatsApp Media Header templates instead of requiring a public URL

Is your feature or enhancement related to a problem? Please describe. Currently, when sending a WhatsApp Cloud API message template that includes a media header (DOCUMENT, IMAGE, or VIDEO), the Chatwoot UI (TemplateParser.vue) only renders a plain text input requiring the agent to manually paste an external, publicly accessible HTTPS URL (media_url). In real-world support and sales workflows, human agents have files (such as invoices, quotes in PDF, or product images) stored locally on their computers. Forcing agents to upload a local PDF/image to an external hosting service or public S3 bucket just to copy and paste a public link into the template modal creates significant operational friction and slows down response times. Describe the solution you'd like Allow agents to upload or drag-and-drop a local file (<input type="file">) directly inside the WhatsApp Template modal when the selected template has a HEADER component with format DOCUMENT, IMAGE, …