Add phase 3: comments and cooking mode

- Comments on visible recipes; author and admin may delete; per-user
  hourly rate limit (COMMENT_RATE_LIMIT_PER_HOUR)
- Cooking mode with large text, tick-off checklists, serving scaling and
  Screen Wake Lock to keep the display on
- Serving calculator auto-submits on change
- Privacy tests cover comment and cooking-mode URLs

Co-Authored-By: Claude Opus 5.5 <[email protected]>

static/js/app.js

@@ -18,3 +18,24 @@ document.addEventListener("change", (event) => {
   const input = event.target.closest(".servings input[name=portionen]");
   if (input && input.value) input.form.requestSubmit();
 });
+
+// Cooking mode: keep the screen on while the page is visible (Screen Wake Lock API).
+(() => {
+  const page = document.querySelector("[data-wakelock]");
+  if (!page || !("wakeLock" in navigator)) return;
+  const status = page.querySelector(".wakelock-status");
+  let lock = null;
+  const acquire = async () => {
+    try {
+      lock = await navigator.wakeLock.request("screen");
+      if (status) status.hidden = false;
+      lock.addEventListener("release", () => { if (status) status.hidden = true; });
+    } catch {
+      // Not allowed right now (e.g. battery saver); the page still works.
+    }
+  };
+  document.addEventListener("visibilitychange", () => {
+    if (document.visibilityState === "visible") acquire();
+  });
+  acquire();
+})();