[February 18, 2026] fix rental price feed signing with correct parcl_id

v0.40.1

Fix Rental Price Feed Signing

• Fixed the /v1/price_feed_rentals/latest endpoint to sign rental prices with the rental parcl_id (base + 2B offset) instead of the raw database parcl_id. This ensures the Ed25519 signature matches the on-chain rental price feed's parcl_id, preventing Ed25519MessageMismatch errors during oracle price updates.
• This also closes a cross-submission vulnerability where a sales-signed price could have been submitted to a rental price feed (or vice versa), since both previously used the same parcl_id in the signed message.