Code-review follow-up: /recompute hardcoded price_source="objective_district_median"
for any body-supplied market_price_per_sqm, mislabeling the honesty-flag once
Stage 2b forwards a price whose genuine source differs (objective_geo_radius /
district_reference / class_norm from financial_estimate).
- schemas/concept.py: add optional price_source: str | None to MassingProgram.
- api/v1/concepts.py: on FAST path use payload.price_source if provided, else the
default label (now a module-level constant _DEFAULT_PRERESOLVED_SOURCE). DB-fallback
and class-norm paths keep their own resolved source unchanged.
- tests: assert body-provided price_source echoes through to financial.price_source
(not overwritten), and the default label applies when the front omits it.