Support sending in-app notifications via the in-app widget

Description: Add native support to create and deliver in-app notifications that appear within the existing in-app widget. This enables timely announcements, roadmap updates, and feedback prompts directly inside the product experience. Problem: There is currently no built-in way to notify users in-app through the widget. This makes it difficult to drive engagement with roadmap items and feedback discussions without resorting to email or separate tools, which are less contextual and can reduce response rates. Benefit: In-app notifications inside the widget provide immediate, contextual communication aligned to the product experience. This increases visibility of updates and participation in feedback discussions while keeping the focus on in-app workflows rather than bug or customer support processes.