fix(members): link sponsors to bills and fix member search

- Poller now fetches bill detail on insert to get sponsor (list endpoint
  has no sponsor data)
- Add backfill_sponsor_ids task + admin endpoint + UI button to fix the
  1,616 existing bills with NULL sponsor_id
- Member name search now matches both "Last, First" and "First Last"
  using split_part() on the stored name column; same fix applied to
  global search
- Load Bill.sponsor relationship eagerly in get_member_bills to prevent
  MissingGreenlet error during Pydantic serialization
- Remove .trim() on search onChange so spaces can be typed

Authored-By: Jack Levy

frontend/app/members/page.tsx

@@ -32,7 +32,7 @@ export default function MembersPage() {
             type="text"
             placeholder="Search by name..."
             value={q}
-            onChange={(e) => { setQ(e.target.value.trim()); setPage(1); }}
+            onChange={(e) => { setQ(e.target.value); setPage(1); }}
             className="w-full pl-9 pr-3 py-2 text-sm bg-card border border-border rounded-md focus:outline-none"
           />
         </div>