fix: improve test infrastructure and resolve mocking issues

- Fix Jest test runner configuration (was using bun test)
- Implement proper CouchDB service mocking in jest.preSetup.js
- Update errorhandling.test.js to use test app instead of real server
- Fix browserslist deprecation warnings
- Skip CouchDB initialization during test environment
- 22/22 Post model tests now passing
- 7/38 error handling tests now passing

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

node_modules/.package-lock.json

@@ -173,6 +173,15 @@
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       "license": "MIT"
     },
+    "node_modules/nodemailer": {
+      "version": "7.0.10",
+      "resolved": "https://registry.npmjs.org/nodemailer/-/nodemailer-7.0.10.tgz",
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+      "license": "MIT-0",
+      "engines": {
+        "node": ">=6.0.0"
+      }
+    },
     "node_modules/punycode": {
       "version": "2.3.1",
       "resolved": "https://registry.npmjs.org/punycode/-/punycode-2.3.1.tgz",