Harden deploy migration ordering around Django Sites and allauth tables

[tystar86]

Imported from Linear: TYS-167

Source: docs/developers/START_HERE.md → ## Common Pitfalls

Production deploys currently run ensure_sites_migrations before migrate because the app has had ordering issues involving Django Sites and allauth socialaccount tables.

Goal:

• Make deployment ordering reliable and well understood.
• Capture the reason for the current sequencing and reduce the chance of migration-order regressions.

Acceptance ideas:

• Deployment docs or automation clearly describe the required order.
• The risk around Sites/allauth migration ordering is either eliminated or well guarded.

[tystar86]

Closing — this work landed in PR #19 (TYS-167).