chore: remediate pygienium audit findings

Dead code: 77 verified-unused exports, files (BackArrow, MenuBars,
cookies.ts, db/create.ts, schemas/comment.ts, security-headers.ts) and
12 unused dependencies removed
Comments: ~370 RESTATE comments stripped across 53 files; 2 verbose
blocks tightened; dead commented-out config removed
Complexity: bulkUpsert extracted into 11 per-entity helpers (CCN 156->~10);
login formHandler split into 3 submitters (CCN 63->~5); account page render
split into 8 section components (CCN 40); updatePost SQL builder rebuilt;
assert*Owned consolidated behind generic assertOwnedBy
Defensive guards: 4 redundant rethrow/nullish guards removed

src/components/blog/PostSorting.tsx

@@ -100,7 +100,7 @@ export default function PostSorting(props: PostSortingProps) {
       case "newest":
         break; // Posts already come newest first from DB (DESC order)
       case "oldest":
-        sorted.reverse(); // Reverse to get oldest first
+        sorted.reverse();
         break;
       case "most_liked":
         sorted.sort((a, b) => (b.total_likes || 0) - (a.total_likes || 0));