[Feature]: Validation report  #77

What type of issue is this?

• Bug report
• Feature request

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the reqifviewer
• I have searched open and closed issues to ensure it has not already been reported

Description

Acceptance criteria

• On load, optionally validate against the ReqIF schema (ReqIFSharp validate: true with a handler) and list the problems with line numbers.
• Extra checks: duplicate identifiers, references to missing elements, unused types and datatypes.
• A badge in the header shows the result; the overview links to the report.

Steps to Reproduce

NA

System Configuration

• reqifviewer version: 6.1.0 (development, with [Refactor] Blazor Blueprint app shell and Blazor Web App hosting #56)
• Environment (Operating system, version and so on): Windows 11, Chrome
• .NET Framework version: .NET 10
• Additional information: Plan item R-11 of the viewer improvement plan. Size: M.