[BUG] GitHub OAuth Callback URL Forcing HTTPS Despite HTTP Configuration

**GitHub OAuth Callback URL Forcing HTTPS Despite HTTP Configuration**

I want to deploy my app using HTTP.
The callback URL for GitHub OAuth still supports HTTP.
However, even if I set the callback URL to use HTTP, the `redirect_uri` is automatically changed to HTTPS when returned by the `redir_url` function.
I attempted to use the `scheme` parameter of `redir_url`, but it doesn’t work when `host="0.0.0.0"`.
(Temporarily using the `replace` syntax resolves the issue.)

I understand that HTTPS is the standard, but I wanted to report this behavior. Below is the code I used.

```python
# User asks us to Login
@app.get("/login")
def login(request):
redir = redir_url(request, auth_callback_path, "http") # .replace("https", "http")
login_link = client.login_link(redir)
return login_page(login_link)

# User comes back to us with an auth code from Github
@app.get(auth_callback_path)
def auth_redirect(code: str, request, session):
redir = redir_url(request, auth_callback_path, "http") # .replace("https", "http")
user_info = client.retr_info(code, redir)
user_id = user_info[client.id_key]
session["user_id"] = user_id

if user_id != authorized_user_id:
return RedirectResponse("/protected", status_code=303)
return RedirectResponse("/", status_code=303)

@app.get("/protected")
async def protected(req):
return not_authorized_page()

serve(host="0.0.0.0", port=8050, reload=(not ENV_MODE))
```

**Expected behavior**
```
redir = redir_url(request, auth_callback_path, “http”)
```
I hope the syntax works.

**Environment Information**
Please provide the following version information:
- fastlite version: 0.0.13
- fastcore version: 1.7.22
- fasthtml version: 0.10.1