Empty catch blocks silently swallow exceptions in async flows

[rido-min]

Summary

Several async code paths use empty catch { } blocks that silently swallow exceptions, making failures invisible and debugging difficult.

Locations

File	Line	Context
Teams.Apps/App.cs	302-303	Token retrieval failure silently ignored
Teams.Apps/Contexts/Context.SignIn.cs	71	OAuth token exchange failure silently ignored
Plugins.External.McpClient/McpClientPlugin.cs	137-145	All exceptions from Task.WhenAll swallowed (comment says handled later, but pattern is fragile)

Impact

• Authentication/token failures become invisible — users see downstream errors with no root cause
• OAuth flow failures are masked — sign-in silently fails without any indication of why
• MCP tool fetching errors could be lost if the downstream handling has bugs

Suggested fix

At minimum, log the exception before suppressing it. Where the exception represents a recoverable condition, catch the specific exception type rather than using a bare catch. Where the intent is "try but don't fail", use a pattern like:

catch (Exception ex) when (LogAndSuppress(ex))
{
}

or simply:

catch (Exception ex)
{
    _logger.Warning("Token retrieval failed, proceeding without token", ex);
}