[Feature]: Document overview instead of Statistics  #75

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

Today the statistics page shows a counter per ReqIF element type. It does not say anything about the content: how many requirements per specification, how complete the attributes are, which requirements have no traces, or whether the file is valid.

Acceptance criteria

• After loading, the user lands on an overview: title, source tool, dates; one card per specification with requirement counts; trace coverage; attribute fill rate per type (chart); attachments count; validation status ([Feature]: Validation report  #77).
• Each figure links to the filtered view behind it.

Steps to Reproduce

Load requirements-and-objects.reqifz or ProR_Traceability-Template-v1.0.reqif (reqifviewer.Tests/TestData) and look at the pages mentioned above.

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-09 of the viewer improvement plan. Size: M.