feat: render app version in bottom-left footer

src/components/ui/VersionFooter.vue

@@ -0,0 +1,13 @@
+<script setup lang="ts">
+const version = typeof __APP_VERSION__ !== "undefined" ? __APP_VERSION__ : "dev";
+</script>
+
+<template>
+  <div
+    class="fixed bottom-2 left-2 text-xs font-mono text-gray-50/40 hover:text-gray-50/80 transition-opacity pointer-events-none select-none z-10"
+    :title="`P2Pix ${version}`"
+    aria-label="Application version"
+  >
+    v{{ version }}
+  </div>
+</template>