fix: initialize default SSO URL before saving

[sagarkt]

Summary

• initialize new and legacy-empty SSO configurations with the current orchestrator URL
• keep the URL shown in the form synchronized with the state validated by Save
• clear the required-field error when the suggested URL is selected

Problem

The SSO form historically rendered the orchestrator URL as a fallback while leaving ssoConfig.url empty. Save validates ssoConfig.url, so an apparently populated form failed with "Some required field are missing" until the user clicked the suggested URL. The YAML editor's inner connector config was not the missing field.

Testing

• git diff --check
• Reviewed both default-empty and previously saved custom URL paths
• Full TypeScript/ESLint checks could not complete locally because Yarn stalled while linking the dependency tree; PR CI should run the canonical checks

Fixes devtron-labs/devtron#6312