Alerts: Make error messages in Allocation of Emissions page display after action

#### Describe the task

Make the error messages in the Allocation of Emissions page display only after clicking `Save` or `Save & Continue`

Error messages:
- `All emissions must be allocated to 100% before saving and continuing`
- `A methodology must be selected before saving and continuing`

Currently, these messages show up immediately on the page and only disappear if/when you have selected a methodology and filled out the allocation to 100%.

This ticket is to fix this so that the messages ONLY display if you try and save/save & continue without a methodology and/or 100% allocation.

#### Acceptance Criteria

- [ ] first
- [ ] second
- [ ] third

#### Definition of Done

- [ ] first
- [ ] second
- [ ] third

#### Additional context

- Add any other context about the task here.
- Or here

Start at the Allocation of Emissions page and trace how the methodology and 100% allocation validations are rendered and triggered. Reproduce the page with missing values, then use Save and Save & Continue to confirm each relevant error appears only after those actions and disappears when the inputs are valid.

Written by the indexing model from the issue text.