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/util/AutoScroll.vue

@@ -0,0 +1,78 @@
+<template>
+    <div ref="container" @mouseover="handleHover" class="overflow-y-auto">
+        <slot />
+    </div>
+</template>
+
+<script setup>
+import { useTemplateRef, onMounted, onBeforeUnmount } from "vue";
+
+const container = useTemplateRef("container");
+
+const SPEED = 0.0005; // % per frame
+const PAUSE = 2000; // ms at top/bottom
+
+let pos = 0;
+let direction = 1; // 1 = down, -1 = up
+let timeoutId;
+let timeoutId2;
+let cachedScrollHeight = 0;
+
+function measureScrollHeight() {
+    const el = container.value;
+    if (el) cachedScrollHeight = el.scrollHeight;
+}
+
+function handleHover() {
+    cancelAnimationFrame(timeoutId);
+    clearTimeout(timeoutId2);
+    timeoutId2 = setTimeout(
+        () => (timeoutId = requestAnimationFrame(tick)),
+        PAUSE,
+    );
+}
+
+function tick() {
+    const el = container.value;
+    if (!el || cachedScrollHeight === 0) {
+        timeoutId = requestAnimationFrame(tick);
+        return;
+    }
+
+    const reachedBottom = pos <= 0;
+    const reachedTop = pos >= 1;
+
+    if (reachedBottom) {
+        pos = 0.001;
+        direction = 1;
+        handleHover();
+        return;
+    } else if (reachedTop) {
+        pos = 0.999;
+        direction = -1;
+        handleHover();
+        return;
+    }
+
+    pos += direction * SPEED;
+
+    el.scrollTop = pos * cachedScrollHeight;
+
+    timeoutId = requestAnimationFrame(tick);
+}
+
+let resizeObserver;
+
+onMounted(() => {
+    measureScrollHeight();
+    timeoutId = requestAnimationFrame(tick);
+
+    resizeObserver = new ResizeObserver(measureScrollHeight);
+    resizeObserver.observe(container.value);
+});
+
+onBeforeUnmount(() => {
+    cancelAnimationFrame(timeoutId);
+    resizeObserver?.disconnect();
+});
+</script>