Add .NET 8 root infrastructure (global.json + Directory.Build.props)

[devin-ai-integration]

Summary

Adds two repo-root infrastructure files in support of the broader .NET 8 upgrade work happening across this repo. No .csproj, .sln, or source files are touched.

Files added

global.json

{"sdk":{"version":"8.0.300","rollForward":"latestFeature"}}

Pins the .NET SDK to 8.0.300 with rollForward: latestFeature, so any 8.0.x SDK ≥ 8.0.300 is acceptable but no .NET 9+ SDK will be silently picked up.

Directory.Build.props

<Project>
  <PropertyGroup>
    <LangVersion>latest</LangVersion>
  </PropertyGroup>
</Project>

Sets LangVersion=latest for every project in the repo. Kept minimal on purpose — no <Nullable> or <ImplicitUsings> because legacy (.NET Framework, older TFM) projects still live in this repo and would break under those settings.

Code changes

None. Diff is exactly the two new root-level files.

Build / verification

After installing the .NET 8 SDK on a clean VM via dotnet-install.sh --version 8.0.300:

$ dotnet --version
8.0.300

$ dotnet --list-sdks
8.0.300 [/home/ubuntu/.dotnet/sdk]

$ dotnet build AspNetCore/Razor-Mvc/Razor.AdvancedSearch/EqDemo.AspNetCoreRazor.AdvancedSearch.csproj
...
Build succeeded.
    0 Warning(s)
    0 Error(s)
Time Elapsed 00:00:16.47

This confirms:

1. global.json resolves to a real, installed SDK.
2. Directory.Build.props is picked up automatically and does not break a representative net8.0 project.

No .csproj/lockfile/build-artifact changes from that test build were committed — bin/ and obj/ are gitignored, so the PR diff is exactly the two files described above.

Review & Testing Checklist for Human

Risk: green (config-only, no source changes).

• Verify the PR diff shows only global.json and Directory.Build.props at the repo root (no .csproj, .sln, or source file changes).
• Confirm 8.0.300 is an acceptable floor for everyone working on this repo. With rollForward: latestFeature, any 8.0.x ≥ 8.0.300 will satisfy it; .NET 9+ SDKs will be rejected.
• Sanity-check that no project in the repo currently relies on a <LangVersion> lower than latest (very unlikely to be a problem in practice — latest is permissive).

Notes

• global.json is intentionally a single-line file matching the exact content specified by the parent task.
• This PR is intended to land alongside (or before) the per-project .NET 8 upgrade PRs being prepared in parallel by other sessions.

Link to Devin session: https://app.devin.ai/sessions/0fb1d9c0e883407cbd9e16cf3f81dbca
Requested by: @tobydrinkall

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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