New Decision Meeting Tool

[chris263]

Description

This pull request adds the new Decision Meeting Tool, designed to support breeding teams during advancement and selection meetings. The tool provides a centralized interface to review accessions, evaluate available data, record decisions, and save meeting outcomes in a structured and reproducible way.

With this feature, users can:

create and manage decision meetings
associate meetings with breeding programs and datasets
review accession-level information relevant to decision making
assign decisions such as advance, drop, hold, or jump
capture notes and comments during the discussion
save decisions in JSON format for traceability and later retrieval
generate meeting reports for documentation and communication

Fixes #5732
Fixes #5460

[isaak]

-- When creating a meeting:

1. When adding attendees, it seems to list all database users. Are the users filtered by the breeding program the creator of the meeting belongs to?

2. I think it may be easier to see if the validation errors are at the bottom of the dialog box, instead of at the top which is out of view.

[lukasmueller]

This pull request seems to contain a lot of changes unrelated to the new decision meeting tool, including the addition of populations to the wizard and many changes to the trial tree view. It would be preferable to have only the changes related to the new function in this pull request.