fix: Restore make docker-up

[khvn26]

Thanks for submitting a PR! Please check the boxes below:

• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

Restores the docker-up Make target removed in #4747. Adds conventional file name and a bit of documentation.

How did you test this code?

Ran make docker-up test to verify the local Postgres db is created correctly.

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3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)	Visit Preview		Dec 10, 2024 0:56am
flagsmith-frontend-preview	⬜️ Ignored (Inspect)	Visit Preview		Dec 10, 2024 0:56am
flagsmith-frontend-staging	⬜️ Ignored (Inspect)	Visit Preview		Dec 10, 2024 0:56am

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-4907	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-4907	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-4907	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-4907	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-4907	Finished ✅	Results ✅

[github-actions]

Uffizzi Preview deployment-58976 was deleted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.38%. Comparing base (05ab7cf) to head (3e20fd7).
Report is 17 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4907   +/-   ##
=======================================
  Coverage   97.38%   97.38%           
=======================================
  Files        1189     1189           
  Lines       41420    41453   +33     
=======================================
+ Hits        40338    40371   +33     
  Misses       1082     1082           

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