docs(toolbar): Update @sentry/toolbar docs to include help for CSP issues (#13979)

New content look like this:
<img width="946" alt="SCR-20250609-siky"
src="https://github.com/user-attachments/assets/b3b12fe9-3f07-4a42-a866-61f4f506f957"
/>
<img width="909" alt="SCR-20250609-simp"
src="https://github.com/user-attachments/assets/16cd089a-dd95-4b66-8cee-f009fd1b34f2"
/>


Related to getsentry/sentry#93206
Related to
getsentry/sentry-options-automator#4119

Author: ryan953

docs/product/sentry-toolbar/faq.mdx

@@ -50,7 +50,18 @@ useSentryToolbar({
   },
 })
 ```
+</Expandable>
+
+<Expandable permalink title="Why is the Toolbar stuck saying 'Connecting to ...'?">
+
+If you're seeing the message "Connecting to ...' in the Toolbar, it means that the Toolbar is unable to connect to the Sentry server. This can happen for a few reasons:
+
+1. Check your browser console for a message like `Refused to frame 'https://my-org.sentry.io/toolbar/sentry/javascript/iframe/' because it violates the following Content Security Policy directive: "frame-src 'self'".` This means your site is not allowing the toolbar's iframe to load. To fix this you can add your sentry domain into the [`frame-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-src) directive in your CSP. The result would be a response header that says `Content-Security-Policy: frame-src my-org.sentry.io;`
 
+2. The Sentry server is down or unreachable. If this is the case check the following:
+    - Check the [Sentry status page](https://status.sentry.io/) to see if there are any issues.
+    - If the Sentry server is down, you can try again later.
+    - If the Sentry server is unreachable, you can try again later.
 </Expandable>
 
 <Expandable permalink title="Are there plans to include the Toolbar in the JavaScript SDK?">

docs/product/sentry-toolbar/setup.mdx

@@ -21,6 +21,8 @@ You will need to edit the [Project Settings](https://sentry.io/orgredirect/organ
 
 ![Sentry's Toolbar Settings Page](./img/sentry-project-settings-toolbar.png)
 
+You may also need to add your Sentry domain to the [`frame-src`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-src) directive in your CSP response headers. See the [FAQ: _"Why is the Toolbar stuck saying 'Connecting to ...'?"_](/product/sentry-toolbar/faq/#why-is-the-toolbar-stuck-saying-connecting-to-) for more information.
+
 ## 2. Install
 
 If you are developing a React based application, it's time to add the Toolbar into your `package.json` file.