The admin program-edit form sends null for empty number inputs.
ProgramCreate had minimum_purchase_cents declared as int (default
0, ge=0), which rejected null with 422 — even though the DB column
is NOT NULL with default 0 and "0 means no minimum" is the
documented semantics.
Add a field_validator(mode="before") that coerces None to 0 so
the admin form (and any other client that sends null for an empty
optional number) goes through cleanly. The other tolerant fields
in the schema (stamps_reward_value_cents, points_expiration_days)
are already int | None; ProgramUpdate already accepts null here.
User hit this after a clean-DB reset prevented falling back to a
pre-existing program; the merchant area form happens to send 0
instead of null, masking the bug there.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>