chore: add the Rust workspace

This repo holds both languages, so it needs both workspaces. Layout is the same
rule on each side — apps/ for what runs, crates/ and packages/ for what is
shared, split by what a thing is rather than what it is written in.

Members are empty because nothing has moved in yet. Versions are pinned once at
the root so two crates cannot disagree about a dependency.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -8,6 +8,10 @@ node_modules
 .svelte-kit
 build
 
+# Rust
+/target
+**/*.rs.bk
+
 # OS
 .DS_Store
 Thumbs.db