feat(analytics): Plausible über PLAUSIBLE_ENABLED und PLAUSIBLE_HOST steuerbar

Runtime-Konfiguration im Frontend-Container trennt Prod und Staging;
Staging deaktiviert Analytics standardmäßig.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/public/plausible-bootstrap.js

@@ -0,0 +1,25 @@
+/**
+ * Loads Plausible when enabled via /runtime-config.json (from .env in Docker / Vite dev).
+ * data-domain is always the current hostname (prod vs staging).
+ */
+(function () {
+  function load(cfg) {
+    if (!cfg || !cfg.plausibleEnabled || !cfg.plausibleHost) return
+    var host = String(cfg.plausibleHost).replace(/\/$/, '')
+    if (!host) return
+    var s = document.createElement('script')
+    s.defer = true
+    s.dataset.domain = window.location.hostname
+    s.src = host + '/js/script.tagged-events.js'
+    document.head.appendChild(s)
+  }
+
+  fetch('/runtime-config.json', { cache: 'no-store' })
+    .then(function (r) {
+      return r.ok ? r.json() : null
+    })
+    .then(load)
+    .catch(function () {
+      /* analytics optional */
+    })
+})()