Extract Vue frontend into separate container and add stp_wasm crate

Move Vue app from nginx/vue/ to top-level vue/ with its own Dockerfile,
update docker-compose configs and nginx proxy to serve from the new
container, and add initial Rust WASM crate (stp_wasm). Also fix .gitignore
to exclude Rust target/ directories.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vue/crates/stp_wasm/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "stp_wasm"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+js-sys = "0.3.85"
+wasm-bindgen = "0.2.108"
+web-sys = { version = "0.3.85", features = [
+  "console",
+  "Document",
+  "Element",
+  "Window",
+  "Animation",
+] }