SQLAlchemy 2.0 defaults to mapping Python enum *names* (OPEN, CLOSED)
to DB values, but MySQL stores lowercase *values* (open, closed).
This mismatch causes LookupError on read.
Adding values_callable=lambda x: [e.value for e in x] tells SQLAlchemy
to use the enum values for DB mapping.
Affected models: milestone, task, meeting, propose, support
- New Propose model (app/models/propose.py) with status enum (open/accepted/rejected)
- New Propose schemas (ProposeCreate/Update/Response) in schemas.py
- MySQL enum migration in main.py for milestone/task status columns
- milestone: pending→open, deferred→closed, progressing→undergoing
- task: progressing→undergoing
- Import propose model in startup for create_all
- Add started_at column migration for milestones
