Add initial documentation and test placeholders

- Comprehensive README.md with run instructions
- Backend test structure (server.test.js)
- Frontend test structure (App.test.js)
- Setup instructions and troubleshooting guide
- API documentation and project structure overview

frontend/src/__tests__/App.test.js

@@ -0,0 +1,53 @@
+/**
+ * Placeholder test file for Line of Sight Frontend
+ * 
+ * TODO: Add real tests for:
+ * - Map component rendering
+ * - Direction selector functionality
+ * - API integration
+ * - User interactions
+ * - Line of sight visualization
+ */
+
+describe('Line of Sight Frontend', () => {
+  describe('App Component', () => {
+    test('should render map container', () => {
+      // TODO: Implement component rendering test
+      expect(true).toBe(true);
+    });
+
+    test('should display direction selector', () => {
+      // TODO: Implement direction selector test
+      expect(true).toBe(true);
+    });
+
+    test('should handle map click events', () => {
+      // TODO: Implement click event test
+      expect(true).toBe(true);
+    });
+  });
+
+  describe('API Integration', () => {
+    test('should fetch line of sight data', () => {
+      // TODO: Implement API fetch test
+      expect(true).toBe(true);
+    });
+
+    test('should handle API errors gracefully', () => {
+      // TODO: Implement error handling test
+      expect(true).toBe(true);
+    });
+  });
+
+  describe('UI Components', () => {
+    test('should toggle map style between light/dark', () => {
+      // TODO: Implement style toggle test
+      expect(true).toBe(true);
+    });
+
+    test('should display conurbation results table', () => {
+      // TODO: Implement results table test
+      expect(true).toBe(true);
+    });
+  });
+});