feat(mail/delivery): add error-count based blocking to rate limiter; improve test SMTP server port selection; add tsbuild scripts and devDependency; remove stale backup file

package.json

@@ -32,12 +32,14 @@
   },
   "scripts": {
     "test": "tstest test/ --logfile --verbose --timeout 60",
-    "build": "echo 'no build needed'"
+    "build": "tsbuild tsfolders",
+    "check": "tsbuild check"
   },
   "devDependencies": {
+    "@git.zone/tsbuild": "^2.6.8",
     "@git.zone/tstest": "^2.3.1",
-    "@types/node": "^24.0.10",
     "@types/mailparser": "^3.4.6",
+    "@types/node": "^24.0.10",
     "tsx": "^4.19.2"
   },
   "dependencies": {