UI - Search modal - fix Enter dismissing the form instead of searching (#4428)

Pressing Enter in the search box closed the modal without running the search;
you had to click Search with the mouse.

Implicit form submission fires a click at the submit button, and a
keyboard-synthesised click carries detail 0 and coordinates of 0,0. The
backdrop-click handler only tested the coordinates against the dialog's
bounding box, so 0,0 read as "outside" - it closed the dialog and blanked the
input while the click was still bubbling. By the time the submit ran, `q` was
empty and `required` rejected it, so nothing was searched.

Ignore clicks with detail 0 - only a real pointer can hit the backdrop.

Verified with Chromium against a local instance: Enter now lands on
/?q=<term>, and mouse submit, backdrop click, Escape and Enter-on-empty all
still behave.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

changedetectionio/static/js/search-modal.js

@@ -62,6 +62,15 @@
 
     // Close modal when clicking the backdrop
     searchModal.addEventListener('click', function(e) {
+      // Only real pointer clicks can land on the backdrop. Keyboard-synthesised clicks
+      // report detail 0 and coordinates of 0,0, which the geometry test below reads as
+      // "outside the dialog" - and implicit form submission (Enter in the input) fires
+      // exactly such a click at the Search button. That closed the modal and blanked
+      // the input mid-dispatch, so the submit that followed hit an empty `required`
+      // field and was rejected: Enter appeared to just dismiss the form.
+      if (e.detail === 0) {
+        return;
+      }
       const rect = searchModal.getBoundingClientRect();
       const isInDialog = (
         rect.top <= e.clientY &&