Add pagination/search/sort to the admin tables that can grow large

Uses simple-datatables (vanilla JS, no jQuery needed) on the Users,
Sessions, Email Log, and Feedback tables, since those grow with real
usage. Left Games (small, admin-curated) and Hints (row order is
meaningful - "checked in order" - a sortable column would mislead)
untouched.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -27,6 +27,7 @@
   "dependencies": {
     "@popperjs/core": "^2.11.8",
     "bootstrap": "^5.3.8",
-    "bootstrap-icons": "^1.13.1"
+    "bootstrap-icons": "^1.13.1",
+    "simple-datatables": "^10.3.0"
   }
 }