[TOOL-3090] Dashboard: Add Deprecated alert in Embeds page, UI adjust…

…ments (#5960)

<!-- start pr-codex -->

## PR-Codex overview
This PR focuses on updating the `EmbedSetup` component to enhance user experience by introducing a deprecation alert for NFT embeds, reorganizing the UI layout, and adding new configuration options.

### Detailed summary
- Added an `Alert` component indicating the deprecation of thirdweb NFT Embeds.
- Replaced `Flex` with `div` for layout simplification.
- Consolidated form controls for configuration and added new fields for `Client ID`, `RPC Url`, and `Gasless` options.
- Introduced a theme selection dropdown.
- Updated embed code section and preview area for clarity.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}`

<!-- end pr-codex -->