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/src/components/input/ToggleButton.vue

@@ -0,0 +1,31 @@
+<script setup>
+import { ref } from "vue";
+
+const props = defineProps({
+    modelValue: {
+        type: Boolean,
+        default: false,
+    },
+});
+
+const emit = defineEmits(["update:modelValue"]);
+
+function toggle() {
+    emit("update:modelValue", !props.modelValue);
+}
+</script>
+<template>
+    <button
+        @click="toggle"
+        class="box-content border-2 border-primary w-20 h-fit rounded-full cursor-pointer"
+        :class="[props.modelValue ? 'bg-bg_secondary' : 'bg-bg_primary']"
+    >
+        <svg
+            viewBox="0 0 40 40"
+            class="w-10 h-10 transition-all duration-300 ease-in-out"
+            :class="[props.modelValue ? 'ml-10' : 'ml-0']"
+        >
+            <circle class="fill-primary" cx="20" cy="20" r="20" />
+        </svg>
+    </button>
+</template>