Allow a user to modify precipitation in Fire Behaviour Calculator (old)

**As a** *FBAN* **I want** *to be able to modify the precipitation value in FireBAT* **So That** *if precipitation is forecasted, but does not reflect actual or likely conditions on the morning I'm preparing FBAs, I can ensure my calculations are accurate without doing extra, manual work*

**Additional Context**
- many cases of precip being forecasted but not happening, and it drastically lowers key fire weather indices, meaning a FBA might not be issued, when in reality it should be
- FBANs are aware and monitoring this - it requires more awareness/thinking, manual work, and time to run these calculations manually to override the forecasted precip
- calls with BB and DH on Jul 23 - **DH says prioritize**

Precip influences:
- FFMC (Temp, RH, Wind, Precip)
- DMC (Temp, Precip, Wind)
- DC (Temp, Precip)

How much precip impacts fuels?
- 0.6 mm impacts FFMC
- 1.5 mm impacts DMC
- 2.9 mm impacts DC

Indices impact:
- ISI impacted by FFMC, wind
- BUI impacted by DC
- FWI impacted by ISI, BUI

**Acceptance Criteria**
- [ ] Given I am on FireBAT, When I click a forecasted value in the precip column, Then I can change the value
- [ ] Given I have changed a precip value, Then the row updates with the new calculations

Start by locating the old Fire Behaviour Calculator (FireBAT), the precipitation column, and the row calculation path. Trace how forecast precipitation feeds the FFMC, DMC, DC, ISI, BUI, and FWI values. Done means a forecast precipitation value can be edited and the row recalculates according to the acceptance criteria.

Written by the indexing model from the issue text.