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/AddAttachmentSection.tsx

@@ -63,7 +63,6 @@ export default function AddAttachmentSection(props: AddAttachmentSectionProps) {
             };
             reader.readAsDataURL(file);
 
-            // Refresh the S3 file list
             await loadAttachments();
           }
         } catch (err) {
@@ -81,7 +80,6 @@ export default function AddAttachmentSection(props: AddAttachmentSectionProps) {
         body: JSON.stringify({ key })
       });
 
-      // Refresh the S3 file list
       await loadAttachments();
     } catch (err) {
       console.error("Failed to delete file:", err);