fix(web): repair news ticker custom-feeds save for JSON path

The JS dotToNested() helper converts indexed form fields like
feeds.custom_feeds.0.name into a dict {'0': {name:...}} rather than a
proper array. The form-data path already had fix_array_structures() to
convert those dicts back to arrays before schema validation, but the
JSON path (used by all web-UI saves) never ran that fix, so saving any
custom feed produced a schema validation error: "Expected type array,
got object".

Add _fix_json_arrays() immediately after schema loading on the JSON
path, mirroring the existing fix_array_structures() logic.

Also fix custom-feeds.js getValue() to omit the logo key entirely when
no logo is present instead of returning logo:null, which would fail
schema validation (logo expects type object).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web_interface/static/v3/js/widgets/custom-feeds.js

@@ -54,15 +54,18 @@
                 const logoIdInput = row.querySelector('input[name*=".logo.id"]');
                 
                 if (nameInput && urlInput) {
-                    feeds.push({
+                    const feedObj = {
                         name: nameInput.value,
                         url: urlInput.value,
-                        enabled: enabledInput ? enabledInput.checked : true,
-                        logo: logoPathInput || logoIdInput ? {
+                        enabled: enabledInput ? enabledInput.checked : true
+                    };
+                    if (logoPathInput || logoIdInput) {
+                        feedObj.logo = {
                             path: logoPathInput ? logoPathInput.value : '',
                             id: logoIdInput ? logoIdInput.value : ''
-                        } : null
-                    });
+                        };
+                    }
+                    feeds.push(feedObj);
                 }
             });