Chore: Re-do Landing Page - Remove All Non-essential

At present the landing page of the `imgup` app is:

Please try to remember:

# _Nobody_ Cares What Tech You're Using!

Yes, as an `engineer` you might care.
But the `person` _using_ the App doesn't care for a _millisecond_.
You're just _wasting_ their time with this noise.

The /liveview route: https://imgup.fly.dev/liveview is closer to what we want:

But it's still cluttered and not mobile-first/focussed:

The name of the file I want to upload is below the fold, i.e. I have to scroll to see it.

And there's a pointless `Upload` button that adds friction/steps to the process.
Uploading should be automatic.

# Todo

+ [ ] Remove the option for multiple ways to upload and just
+ [ ] Show a single upload landing page with an upload interface
+ [ ] Remove the "Upload" button
+ [ ] Automatically trigger upload and display thumbnail when the image is selected or dragged in.
+ [ ] Automatically show the thumbnail of the uploaded image as soon as possible.
+ [ ] Add `Copy URL` Button via `JS`: https://github.com/dwyl/imgup/issues/126

Start by inspecting the current landing page and the /liveview route, using the screenshots and Todo list as the acceptance criteria. Confirm that one focused upload interface removes the Upload button, uploads on selection or drag-in, shows the thumbnail promptly, and leaves the Copy URL work to issue #126.

Written by the indexing model from the issue text.