feat: adopt ReconnectModal from design-blazor, delete local copy

[andregoepel]

Summary

Deletes the local ReconnectModal (razor + css + js + its localization test) in favor of the version shipped by AndreGoepel.Design.Blazor (already at 1.6.0, well past the 1.5.0 release that added it). CSS was byte-identical between the two copies; the local copy's JS/markup had drifted — its resume button was missing the components-resume-failed-visible class, so on a failed resume it fell back to location.reload() instead of showing the proper resume-failed UI state the package version has.

Also removed the now-unused Reconnect.* resx keys (the package component sources its own strings from DesignStrings independently) and a stale doc-table mention in TECHNICAL.md.

Note for a follow-up, not this ticket: the local ReconnectModal was never actually referenced anywhere in this repo (MainLayout.razor, EmptyLayout.razor, the sample's App.razor — none render it), confirmed via repo-wide grep and checked against downstream consumers. This is dead code that predates this consolidation, not something introduced by this change. Whether host apps should wire up <ReconnectModal /> from AndreGoepel.Design.Blazor.Components is a separate decision.

Verification

• dotnet csharpier format . clean
• dotnet build — 0 warnings, 0 errors
• dotnet test (non-E2E) — 29 + 5 + 88 + 3 = 125 passing
• dotnet list package --vulnerable --include-transitive — clean

Closes #148