🚀 Feature: Agent API security improvements

### 🔖 Feature description

This feature proposes the implementation of critical security and quality-of-life enhancements for the public-facing Agent API. As agents are designed to be embedded and shared, it's essential to provide users with robust tools to control access and prevent abuse.

I propose adding two key features to the agent configuration settings:
1. CORS Origin Whitelisting: An option for users to specify a whitelist of allowed domains. This will ensure that the agent's API can only be called from trusted websites.
2. API Limits: A mechanism to set limits on token usage (or maybe number of requests). This is crucial for protecting against denial-of-service (DoS) attacks and managing the costs associated with LLM calls.

### 🎤 Why is this feature needed ?

Currently, once an agent is made public, its API endpoint is open to the world. This poses significant risks for some users.

### ✌️ How do you aim to achieve this?

The implementation can be broken down into two parts, targeting the backend API and the frontend Agent Advanced section.

1. CORS Origin Whitelisting:

Frontend:
- In the Agent Advanced section, add a new text input field labeled "Allowed Origins". This field should accept a comma-separated list of URLs.

Backend:
- Store the list of allowed origins in the database, associated with the specific agent.
- In the API middleware that handles agent requests, check the incoming request's Origin header if enabled.

2. API Limits

Frontend:
- In the Agent Advanced section, add new text input field labeled "Usage limits"

Backend:
- In the API middleware that handles agent requests, check usage before processing if enabled.

### 🔄️ Additional Information

_No response_

### 👀 Have you spent some time to check if this feature request has been raised before?

- [x] I checked and didn't find similar issue

### Are you willing to submit PR?

None