fix(app): repair web manifest and OAuth errors; fix Windows typings

[Observer-GGboy]

What does this PR do?

• Fix invalid site.webmanifest that caused a manifest parse error in the web UI.
• Improve OAuth error visibility in the connect dialog and include response details for token exchange failures.
• Replace Windows placeholder custom-elements.d.ts files with actual typings in app/enterprise packages.

How did you verify your code works?

• bun turbo typecheck Fixes #8812