Speed up Docker image builds using multi-stage parallel pipelines

[debanjum]

Objective

Improve build speed and size of khoj docker images

Changes

Improve docker image build speeds

Result: ~40% drop to 21mins from 35+mins for full build. ~5mins for rebuilds (as all layers can loaded from cache)

• Decouple web app and server build steps
• Build the web app and server in parallel
• Cache docker layers for reuse across dockerize github workflow runs
  • Split Docker build layers for improved cacheability (e.g separate yarn install and yarn build steps)

Reduce size of khoj docker images

Result: ~34% drop to 4.78Gb from 7.25Gb for default build

• Use an up-to-date .dockerignore to exclude unnecessary directories
• Do not installing cuda python packages for cpu builds

Improve web app builds

• Use consistent mechanism to get fonts for web app
• Make tailwind extensions production instead of dev dependencies
• Make next.js create production builds for the web app (via NODE_ENV=production env var)

[sabaimran]

WOOHOO!!! So excited to have faster build times.