fix: edit and delete buttons now actually fire their handlers

The shared el() helper passed every attr through setAttribute(); for
event handlers like onclick a function value gets stringified into an
attribute the DOM compiles as an expression that is evaluated but never
called - so Bearbeiten/Löschen (wired through el()) were silent no-ops,
while addEventListener-wired buttons (Neuer Datensatz, Sperren) worked.

el() now assigns on*-function attrs as properties (node[k] = v), preserving
the real handler. Verified with a DOM-semantics shim: fixed path fires,
legacy setAttribute path provably compiles but never calls.

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

backend/static/ui.js

@@ -37,6 +37,12 @@ function el(tag, attrs = {}, children = []) {
   for (const [k, v] of Object.entries(attrs)) {
     if (k === "class") node.className = v;
     else if (k === "text") node.textContent = v;
+    else if (k.startsWith("on") && typeof v === "function") {
+      // Event handlers MUST be assigned as properties: setAttribute(k, fn)
+      // stringifies the function ("... => ...") and never binds a listener,
+      // which silently killed the Bearbeiten/Löschen buttons.
+      node[k] = v;
+    }
     else node.setAttribute(k, v);
   }
   for (const child of children) node.appendChild(child);