add 5 day cache to static assets

[bmitchinson]

Description

• Add cache policy to Andi static assets so that they're not reloaded on every page
  • Saves a small amount of bandwidth and stops logo pop in

Reminders:

• If changing elixir code in an "app", did you update the relevant version
  in mix.exs?
• If altering an API endpoint, was the relevant postman collection updated?
  • If a new version of smart_city is being used (new fields on a struct), were the relevant postman collections updated?