MoreCast 2.0: Batch Editing Forecasts

**As a** Weather Forecaster

**I need** to be able to batch edit my forecast values

**So That** I can finish a forecast faster

**Acceptance Criteria**
- [ ] Forecaster can apply an adjustment to the current value of any given weather parameter for the entire column
- [ ] consistent behaviour as the model selector
- [ ] Manual edit per cell: spreadsheet function

**Additional Context**
- TEMP & RH UX component: how much per value?
- Increase/Decrease any column value by +-1, 2, 3, 4, etc.
- Eg. Add 2 degrees Celsius to the Temp column for selected stations

**Definition of Done**
https://github.com/bcgov/wps/wiki/Definition-of-Done

Start by locating the forecast editing interface and the existing model selector behavior. Review how forecast values are edited for individual cells and selected stations, then clarify the adjustment UX and verify that batch changes, per-cell edits, and column-wide updates meet the listed acceptance criteria.

Written by the indexing model from the issue text.