[web] Support single-binary distribution of the server by embedding the assets into the binary

## Feature Request

Support single-binary distribution of the server by embedding the assets into the binary on the web target in full-stack mode.

This allows simple distribution of the server as a single binary, instead of having multiple files in an archive. This for example allows easy self-updating, as only the binary needs to be replaced.

## Implement Suggestion

For example rust-embed could be used for embedding the assets.

There could be a flag `--embed` used during build, which would embed the assets and read from the embedded rust-embed struct, instead of checking DIOXUS_PUBLIC_DIR

It's currently possible to achive this with a [build.rs](https://git.plan.ai/plan-ai/mac-mgmt/-/blob/trunk/daemon/build.rs?ref_type=heads#L58-118) and some tweaking to how dioxus server is launched but this is cumbersome and a native feature would be better