feat: adopt AndreGoepel.Testing.E2E

[andregoepel]

Summary

Replaces the local Infrastructure/ fork (E2EAppFixture, E2ETestBase, PageExtensions core, TestData, Totp, VirtualAuthenticator) with the newly published AndreGoepel.Testing.E2E 1.0.0 — this repo's own copy was one of the three source-of-truth forks that package was extracted from, and is where the mandatory trace-capture-on-failure feature originated.

Design

• New local E2EAppFixture is a parameterless subclass of the package's fixture, configured via E2EAppFixtureOptions (WebResourceName="web", ProvisionAdminButtonText="Create administrator").
• This sample sends no real email — under E2E=true it captures mail itself rather than using MailHog. CapturedEmailClient now implements the package's IEmailLinkSource and is wired in via MailSourceFactory, exactly the extension seam that interface exists for.
• Kept PageExtensions.FilterUsersGridAsync as a local extension on top of the package's core.
• A global using E2EAppFixture = ... alias resolves the name collision between this repo's fixture and the package's own E2EAppFixture base type.
• Trace-capture parity confirmed: the package's E2ETestBase<TFixture> carries this repo's original trace-capture-on-failure logic verbatim (same PLAYWRIGHT_TRACE_DIR env var, same unconditional-on-failure behavior) — nothing lost in the move.

Net: -496/+61 lines.

Verification

• dotnet csharpier format . clean
• dotnet build — 0 warnings, 0 errors
• dotnet test (non-Docker) — 321/321 passing
• dotnet list package --vulnerable --include-transitive — clean

Closes #153