Replace 71 broad `except Exception` blocks in 19 router files with the
specific `peewee.DoesNotExist` exception. GET endpoints that call
`Model.get_by_id()` now only catch the expected DoesNotExist error,
allowing real DB failures (connection errors, etc.) to propagate as
500s rather than being masked as 404s.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>