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>

package.json

@@ -19,6 +19,7 @@
     "open": "^11.0.0",
     "react": "18.3.1",
     "react-dom": "18.3.1",
+    "react-grid-layout": "^2.2.2",
     "rss-parser": "^3.13.0",
     "sqlite": "^5.1.1",
     "sqlite3": "^5.1.7"
@@ -28,6 +29,7 @@
     "@types/node": "^20",
     "@types/react": "^18",
     "@types/react-dom": "^18",
+    "@types/react-grid-layout": "^1.3.6",
     "eslint": "^8",
     "eslint-config-next": "14.2.15",
     "tailwindcss": "^4",