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!

---------

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

src/interface/obsidian/src/chat_view.ts

@@ -1074,9 +1074,9 @@ export class KhojChatView extends KhojPaneView {
         };
 
         let response = await fetch(chatUrl, {
-            method: "GET",
+            method: "POST",
             headers: {
-                "Content-Type": "text/plain",
+                "Content-Type": "application/json",
                 "Authorization": `Bearer ${this.setting.khojApiKey}`,
             },
         })