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>

backend/__tests__/geospatial.test.js

@@ -1,5 +1,5 @@
 const request = require("supertest");
-const app = require("../server");
+const { app } = require("../server");
 const Street = require("../models/Street");
 const User = require("../models/User");
 const couchdbService = require("../services/couchdbService");
@@ -9,9 +9,6 @@ describe("Geospatial Queries", () => {
   let authToken;
 
   beforeAll(async () => {
-    // Initialize CouchDB for testing
-    await couchdbService.initialize();
-
     // Create test user
     testUser = await User.create({
       name: "Test User",
@@ -27,16 +24,15 @@ describe("Geospatial Queries", () => {
     );
   });
 
-  afterAll(async () => {
-    await couchdbService.shutdown();
-  });
-
-  beforeEach(async () => {
-    // Clean up streets before each test
-    const streets = await couchdbService.findByType('street');
-    for (const street of streets) {
-      await couchdbService.deleteDocument(street._id, street._rev);
-    }
+  beforeEach(() => {
+    // Reset mocks before each test
+    couchdbService.findByType.mockResolvedValue([]);
+    couchdbService.findStreetsByLocation.mockResolvedValue([]);
+    couchdbService.createDocument.mockResolvedValue({
+      _id: 'test_street_id',
+      _rev: '1-test',
+      type: 'street'
+    });
   });
 
   describe("Street Creation with Coordinates", () => {