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/server/api/routers/downloads.ts

@@ -36,7 +36,6 @@ async function getLatestDMG(
       throw new Error(`No DMG files found in S3 with prefix ${prefix}`);
     }
 
-    // Filter for .dmg files only and sort by LastModified (newest first)
     const dmgFiles = response.Contents.filter((obj) =>
       obj.Key?.endsWith(".dmg")
     ).sort((a, b) => {
@@ -103,7 +102,6 @@ export const downloadsRouter = createTRPCRouter({
         } else if (input.asset_name === "inputhalo") {
           fileKey = await getLatestInputHaloDMG(client, bucket);
         } else {
-          // Use static mapping for other assets
           fileKey = assets[input.asset_name];
 
           if (!fileKey) {