Add Vision Support (#889)

# Summary of Changes
* New UI to show preview of image uploads
* ChatML message changes to support gpt-4o vision based responses on images
* AWS S3 image uploads for persistent image context in conversations
* Database changes to have `vision_enabled` option in server admin panel while configuring models
* Render previously uploaded images in the chat history, show uploaded images for pending msgs
* Pass the uploaded_image_url through to subqueries
* Allow image to render upon first message from the homepage
* Add rendering support for images to shared chat as well
* Fix some UI/functionality bugs in the share page
* Convert user attached images for chat to webp format before upload
* Use placeholder to attached image for data source, response mode actors
* Update all clients to call /api/chat as a POST instead of GET request
* Fix copying chat messages with images to clipboard

TLDR; Add vision support for openai models on Khoj via the web UI!

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Co-authored-by: sabaimran <narmiabas@gmail.com>
Co-authored-by: Debanjum Singh Solanky <debanjum@gmail.com>

src/interface/desktop/shortcut.html

@@ -407,7 +407,7 @@
                 ? `&region=${region}&city=${city}&country=${countryName}&timezone=${timezone}`
                 : '';
 
-            const response = await fetch(chatApi, { headers });
+            const response = await fetch(chatApi, { method: 'POST', headers });
 
             try {
                 if (!response.ok) throw new Error(response.statusText);