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>

lib/db.ts

@@ -80,5 +80,23 @@ export async function getDb() {
     );
   }
 
+  // Migrate existing non-ISO pub_date values to ISO 8601
+  try {
+    const rows = await db.all(
+      "SELECT id, pub_date FROM rss_items WHERE pub_date IS NOT NULL AND pub_date NOT LIKE '____-__-__T%'"
+    );
+    for (const row of rows) {
+      const d = new Date(row.pub_date);
+      if (!isNaN(d.getTime())) {
+        await db.run('UPDATE rss_items SET pub_date = ? WHERE id = ?', d.toISOString(), row.id);
+      }
+    }
+    if (rows.length > 0) {
+      console.log(`Migrated ${rows.length} rss_items pub_date values to ISO 8601`);
+    }
+  } catch (e) {
+    // Table may not have data yet, ignore
+  }
+
   return db;
 }