Add `jiraProjectKey` and `discordChannelId` to the `Project` schema

[abdotop]

Depends on: none

Extend the Project type/collection so a project can be scoped to a Jira
project and a Discord channel. repositoryUrl already exists and covers
GitHub.

Acceptance criteria

• jiraProjectKey?: string and discordChannelId?: string added to
  the Project schema
• Existing projects still load with these fields absent/optional