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/Dockerfile

@@ -0,0 +1,7 @@
+FROM node:22-slim
+RUN apt-get update && apt-get install -y make git && rm -rf /var/lib/apt/lists/*
+WORKDIR /app
+COPY package.json package-lock.json ./
+RUN npm ci
+COPY . .
+CMD ["sh", "-c", "npm run build -- --outDir /output --emptyOutDir"]