refactor(config): rewrite config parser

This PR refactors the configuration parser, replacing the old parser implementation with a new, more structured approach that includes validation and improved organization.

Key changes:
- Complete rewrite of the configuration parser using a map-based structure with built-in validation
- Addition of comprehensive validator functions for configuration values
- Renamed numerous configuration getter methods for better consistency

internal/ui/oauth2.go

@@ -16,6 +16,6 @@ func getOAuth2Manager(ctx context.Context) *oauth2.Manager {
 		config.Opts.OAuth2ClientID(),
 		config.Opts.OAuth2ClientSecret(),
 		config.Opts.OAuth2RedirectURL(),
-		config.Opts.OIDCDiscoveryEndpoint(),
+		config.Opts.OAuth2OIDCDiscoveryEndpoint(),
 	)
 }