Add solidweb.app to default servers #33

Request

Add `solidweb.app` alongside the existing default servers (`solidweb.org`, `solidcommunity.net`, `solid.social`) so users on that provider see a global chat out of the box.

Where it's wired today

`src/chatListPane.js:64-78` — `DEFAULT_CHATS` array:

```js
const DEFAULT_CHATS = [
{ uri: 'https://solid-chat.solidweb.org/public/global/chat.ttl', title: 'Solid Chat Global (solidweb.org)', … },
{ uri: 'https://solid-chat.solidcommunity.net/public/global/chat.ttl', title: 'Solid Chat Global (solidcommunity.net)', … },
{ uri: 'https://solid-chat.solid.social/public/global/chat.ttl', title: 'Solid Chat Experimental', … },
];
```

Proposed change

Add a fourth entry following the same convention:

```js
{
uri: 'https://solid-chat.solidweb.app/public/global/chat.ttl',
title: 'Solid Chat Global (solidweb.app)',
lastMessage: 'Welcome!',
timestamp: '2026-05-17T12:00:00Z'
}
```

Prereqs

• A `solid-chat` account exists on `solidweb.app` with `/public/global/chat.ttl` seeded and public-readable, the same way the other servers are set up

• If solidweb.app uses CSS (WebSocketChannel2023 for live updates), the `index.html:444` host check should be extended to recognize it. Currently:

  ```js
  if (url.host.endsWith('solidcommunity.net')) { … WebSocketChannel2023 path … }
  ```

  Either generalize to "any CSS-based pod" via capability discovery, or add an OR clause for solidweb.app.

Optional, while we're here

`index.html:249` has a free-text IdP input with placeholder `solidweb.org`. A small quick-pick dropdown of known providers (including solidweb.app) would shave a step for new users — but that's scope-creep; happy to file separately if of interest.