pd: allow bundling the web frontend into the fullnode

This is an experiment towards bundling the web frontend code into the fullnode,
with the goal that users who run `pd` nodes can self-host a complete Penumbra
frontend, on their custom domain with auto-HTTPS, with just one command: `pd start`.

To do this, we

- add a new `zipserve` module in `pd`, which takes a `&'static [u8]` with archive data and produces an `axum::Router`;
- bundle an `assets/{minifront,node_status}.zip` (tracked with git-lfs) into the `pd` crate;
- use `axum::Router::merge` to combine the GRPC and frontend endpoints.

Author: hdevalence

.gitattributes

@@ -1 +1,2 @@
 *.bin filter=lfs diff=lfs merge=lfs -text
+assets/** filter=lfs diff=lfs merge=lfs -text