test: Achieve 100% branch coverage for streak calculation functions

- Add 19 comprehensive test cases for calculateStreak and checkAndAwardAchievements
- Cover all edge cases: empty arrays, consecutive dates, gaps, duplicates, invalid dates
- Set up Jest configuration with Babel and jsdom support
- Use date-fns for consistent date mocking across all tests
- Achieve 100% branch coverage for both target functions

Author: cmarchena

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+  "githubPullRequests.ignoredPullRequestBranches": [
+    "main"
+  ]
+}

babel.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  presets: [
+    ['@babel/preset-env', { targets: { node: 'current' } }],
+    ['@babel/preset-react', { runtime: 'automatic' }]
+  ]
+};

jest.config.js

@@ -0,0 +1,15 @@
+module.exports = {
+  testMatch: [
+    '<rootDir>/src/**/__tests__/**/*.{js,jsx,ts,tsx}',
+    '<rootDir>/src/**/*.{spec,test}.{js,jsx,ts,tsx}',
+    '<rootDir>/tests/**/*.{spec,test}.{js,jsx,ts,tsx}'
+  ],
+  moduleNameMapper: {
+    '\\.(css|less|scss|sass)$': 'identity-obj-proxy'
+  },
+  transformIgnorePatterns: [
+    'node_modules/(?!(date-fns)/)'
+  ],
+  testEnvironment: 'jsdom',
+  setupFilesAfterEnv: ['<rootDir>/src/setupTests.js']
+};