[Docs] ADR + architecture docs for hybrid TS + Symfony stack #90
Description
objective
write architecture docs that explain why/when sheety uses a hybrid typescript + symfony backend model.
scope
- architecture decision record (adr)
- request flow diagrams
- service boundaries + ownership
- migration/rollout plan and rollback strategy
acceptance criteria
- docs are in repo and linked from root readme
- decisions and tradeoffs are explicit
- onboarding section helps new contributors run both stacks
resume evidence
can be cited as technical documentation and architecture communication evidence.