Mining fees are incorrectly included in collaborative sweep transactions

When sending a collaborative sweep transaction it is possible to specify the mining fee as an absolute value in sats/vByte.
For example when selecting 12 sats/vByte in the send input screen it is expected that Jam uses this input and the same value (+/- the fee randomization) can be found in the final transaction.

However, this is not the case and the malfunction has been observed several times and is therefore proven.
It happened again even after reboot of my node.

In the case of the sweep TX shown below, the mining fee was set to 12 sats/vByte. Fee randomisation was set to 10% which resulted in an absolute mining fee range of 12-13.2 sats/vByte. This number was also shown in the payment confirmation.

The final transaction however was sent to mempool with 19.5 sats/vByte.

- Version: v0.2.0
- Platform: Umbrel 0.5.4
- Browser: Safari 17.4

Start by reproducing a collaborative sweep from the send input screen with a 12 sats/vByte fee and 10% randomization, then compare the confirmation value with the final transaction in the mempool. Done means the final mining fee remains within the displayed randomized range; the report provides no source file or test entry point.

Written by the indexing model from the issue text.