Fix RSS time filters and add draggable grid layout

Normalize pub_date to ISO 8601 on insert so SQLite datetime comparisons
work correctly. Migrate existing RFC 2822 dates. Change 1h filter to 12h.
Add react-grid-layout with persistent drag/resize and reset button.

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

monitor.js

@@ -85,6 +85,13 @@ async function setupRssTables(db) {
     }
 }
 
+function normalizeDate(item) {
+    const raw = item.isoDate || item.pubDate;
+    if (!raw) return null;
+    const d = new Date(raw);
+    return isNaN(d.getTime()) ? null : d.toISOString();
+}
+
 async function syncRssFeeds(db) {
     if (!RSSParser) return;
     const parser = new RSSParser({ timeout: 5000 });
@@ -101,7 +108,7 @@ async function syncRssFeeds(db) {
                     feed.id,
                     item.title,
                     item.link,
-                    item.pubDate || item.isoDate || null,
+                    normalizeDate(item),
                     item.creator || item.author || null,
                     (item.contentSnippet || item.content || '').substring(0, 500) || null
                 );