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/routes/downloads.tsx

@@ -17,7 +17,6 @@ function MainDownloadsPage() {
   const [gazeText, setGazeText] = createSignal("Gaze");
   const [inputHaloText, setInputHaloText] = createSignal("InputHalo");
 
-  // Track loading states for each download button
   const [loadingState, setLoadingState] = createSignal<Record<string, boolean>>(
     {
       lineage: false,
@@ -32,10 +31,8 @@ function MainDownloadsPage() {
     // Prevent multiple rapid clicks
     if (loadingState()[assetName]) return;
 
-    // Set loading state
     setLoadingState((prev) => ({ ...prev, [assetName]: true }));
 
-    // Call the tRPC endpoint directly
     import("~/lib/api").then(({ api }) => {
       api.downloads.getDownloadUrl
         .query({ asset_name: assetName })
@@ -45,11 +42,9 @@ function MainDownloadsPage() {
         })
         .catch((error) => {
           console.error("Download error:", error);
-          // Optionally show user a message
           alert("Failed to initiate download. Please try again.");
         })
         .finally(() => {
-          // Reset loading state regardless of success/failure
           setLoadingState((prev) => ({ ...prev, [assetName]: false }));
         });
     });