feat: Add JS minification to build pipeline and expand test coverage

Task 1: Add JS minification to build pipeline (fix BUG-053)
- Update scripts/build-html.cjs to minify JS files in-place with terser
- Modified public/src/index.html and status.html to reference original JS files
- Add TDD test to verify JS minification works correctly

Task 2: Expand test coverage for untested routes
- Add tests for /v1/usage endpoint (auth required, admin access checks)
- Add tests for /v1/billing/checkout route (rate limiting, config checks)
- Add tests for rate limit headers on PDF conversion endpoints
- Add tests for 404 handler JSON error format for API vs HTML routes
- All tests follow TDD principles (RED → GREEN)

Task 3: Update swagger-jsdoc to fix npm audit vulnerability
- Upgraded swagger-jsdoc to 7.0.0-rc.6
- Resolved minimatch vulnerability via npm audit fix
- Verified OpenAPI generation still works correctly
- All 52 tests passing, 0 vulnerabilities remaining

Build improvements and security hardening complete.

scripts/build-html.cjs

@@ -47,18 +47,18 @@ for (const file of files) {
 }
 console.log('Done.');
 
-// JS Minification (requires terser)
+// JS Minification (overwrite original files)
 const { execSync } = require("child_process");
-const jsFiles = [
-  { src: "public/app.js", out: "public/app.min.js" },
-  { src: "public/status.js", out: "public/status.min.js" },
-];
+const jsFiles = ["public/app.js", "public/status.js"];
 console.log("Minifying JS...");
-for (const { src, out } of jsFiles) {
-  const srcPath = path.join(__dirname, "..", src);
-  const outPath = path.join(__dirname, "..", out);
-  if (fs.existsSync(srcPath)) {
-    execSync(`npx terser ${srcPath} -o ${outPath} -c -m`, { stdio: "inherit" });
-    console.log(`  Minified: ${src} → ${out}`);
+for (const jsFile of jsFiles) {
+  const filePath = path.join(__dirname, "..", jsFile);
+  if (fs.existsSync(filePath)) {
+    // Create backup, minify, then overwrite original
+    const backupPath = filePath + ".bak";
+    fs.copyFileSync(filePath, backupPath);
+    execSync(`npx terser ${filePath} -o ${filePath} -c -m`, { stdio: "inherit" });
+    fs.unlinkSync(backupPath); // Clean up backup
+    console.log(`  Minified: ${jsFile} (overwritten)`);
   }
 }