[Feature]: Group the ReqIF structure pages in an "Inspect" section  #79

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 sidebar gives equal weight to reader pages and to ReqIF structure pages (data types and four kinds of spec types). Once the reader views exist, the structure pages are mainly useful to people who build or debug exports.

Acceptance criteria

• One "Inspect" section with a tree of spec types, their attribute definitions and datatypes, with usage counts; the current details pages live under it.
• The sidebar shows the reader views first (overview, specifications, search, traces, attachments) and "Inspect" last.

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-13 of the viewer improvement plan. Size: M. Depends on: [Feature]: Migrate the pages from Radzen to Blazor Blueprint  #62.