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/fetch-utils.test.ts

@@ -12,7 +12,6 @@ import {
 async function testTimeoutError() {
   console.log("\n=== Testing Timeout Error ===");
   try {
-    // This should timeout after 1ms
     await fetchWithTimeout("https://httpbin.org/delay/10", { timeout: 1 });
     console.log("❌ Should have thrown TimeoutError");
   } catch (error) {
@@ -29,7 +28,6 @@ async function testTimeoutError() {
 async function testNetworkError() {
   console.log("\n=== Testing Network Error ===");
   try {
-    // This should fail to connect
     await fetchWithTimeout(
       "https://invalid-domain-that-does-not-exist-12345.com"
     );
@@ -47,7 +45,6 @@ async function testNetworkError() {
 async function testAPIError() {
   console.log("\n=== Testing API Error ===");
   try {
-    // This should return 404
     const response = await fetchWithTimeout("https://httpbin.org/status/404");
     await checkResponse(response);
     console.log("❌ Should have thrown APIError");