Add multi-user support to Khoj and use Postgres for backend storage (#549)

- Adds support for multiple users to be connected to the same Khoj instance using their Google login credentials
- Moves storage solution from in-memory json data to a Postgres db. This stores all relevant information, including accounts, embeddings, chat history, server side chat configuration
- Adds the concept of a Khoj server admin for configuring instance-wide settings regarding search model, and chat configuration
- Miscellaneous updates and fixes to the UX, including chat references, colors, and an updated config page
- Adds billing to allow users to subscribe to the cloud service easily
- Adds a separate GitHub action for building the dockerized production (tag `prod`) and dev (tag `dev`) images, separate from the image used for local building. The production image uses `gunicorn` with multiple workers to run the server.
- Updates all clients (Obsidian, Emacs, Desktop) to follow the client/server architecture. The server no longer reads from the file system at all; it only accepts data via the indexer API. In line with that, removes the functionality to configure org, markdown, plaintext, or other file-specific settings in the server. Only leaves GitHub and Notion for server-side configuration.
- Changes license to GNU AGPLv3

Resolves #467 
Resolves #488 
Resolves #303 
Resolves #345 
Resolves #195 
Resolves #280 
Resolves #461 
Closes #259 
Resolves #351
Resolves #301
Resolves #296

src/interface/desktop/package.json

@@ -10,14 +10,14 @@
   "main": "main.js",
   "private": false,
   "devDependencies": {
-    "electron": "25.8.1"
+    "electron": "25.8.4"
   },
   "scripts": {
     "start": "yarn electron ."
   },
   "dependencies": {
     "@todesktop/runtime": "^1.3.0",
-    "axios": "^1.5.0",
+    "axios": "^1.6.0",
     "cron": "^2.4.3",
     "electron-store": "^8.1.0",
     "fs": "^0.0.1-security"