New env design, more docs, misc updates

[Cloud7050]

Mostly closes #36. Closes #44, closes #49.

Breaking Changes

• Devs will need to update their env files accordingly
  • .env, which is already checked in, should cover most of the necessary config
  • Rename your .env.developments to .env.local. You should be able to delete most if not all of your local config. Refer to the various .example files for what they should now contain.\ Or, refer to the updated READMEs to see which variables are required or optional

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General

• Standardise to new env design for all services.\ We now mirror Vite's design. We essentially have .env checked in, .env.local not checked in, and .env.development.local if needed (also not checked in).\ Refer to the READMEs for full details
• Tidy gitignores, dockerignore

Common

• New @common/utils package to share util functions and constants between all services
  • Contains function to merge env files under the new design. All files should now be updated to this

Frontend

• Clean up temp vite file

User

• Remove jest and related edits

Docs

• Update dev instructions to reflect D3. Include Docker, production steps
• Update obsolete info and move relevant details to the root README instead
• Document new env design, and update variable docs in services
• Document managing dependencies with pnpm
• Add WinNAT troubleshooting steps

[Cloud7050]

Opted for 4 space nested list indentation based on https://stackoverflow.com/a/53867805/11536796. Open to discussion.

[Cloud7050]

WinNAT troubleshooting instructions based on https://stackoverflow.com/a/69129708/11536796. See its linked GitHub issue comments for more context.