feat(billing): refacto billing (#14243)

… prices for metered billing

---------

Co-authored-by: Félix Malfait <felix.malfait@gmail.com>
Co-authored-by: Félix Malfait <felix@twenty.com>

.cursor/rules/testing-guidelines.mdc

@@ -69,6 +69,45 @@ beforeEach(() => {
 - **Keep tests isolated** - Independent and repeatable
 - **70% unit, 20% integration, 10% E2E** - Test pyramid
 
+## Running Tests
+
+### Single Test File Execution
+```bash
+# ✅ Run a specific test file (PREFERRED - Fast & Efficient)
+npx jest path/to/test.test.ts --config=packages/PROJECT/jest.config.mjs
+
+# Key Benefits:
+# - Only runs the specific test file (fast)
+# - No dependency resolution overhead
+# - Immediate feedback for test development
+
+# ✅ Examples:
+# Frontend tests (use .test.ts extension)
+npx jest packages/twenty-front/src/modules/localization/utils/detection/detectNumberFormat.test.ts --config=packages/twenty-front/jest.config.mjs
+
+# Server tests (use .spec.ts extension)
+npx jest packages/twenty-server/src/utils/__test__/is-work-email.spec.ts --config=packages/twenty-server/jest.config.mjs
+
+# ❌ AVOID - This runs ALL tests (slow):
+npx nx test twenty-front --testPathPattern=detectNumberFormat.test.ts
+
+# ✅ Run tests in watch mode for development:
+npx jest path/to/test.test.ts --config=packages/twenty-front/jest.config.mjs --watch
+
+# ✅ Run with coverage for single file:
+npx jest path/to/test.test.ts --config=packages/twenty-front/jest.config.mjs --coverage
+```
+
+### Test Suite Execution
+```bash
+# Run all tests for a project (use sparingly)
+npx nx test twenty-front
+npx nx test twenty-server
+
+# Run tests matching a pattern
+npx jest --testNamePattern="UserService" --config=packages/twenty-front/jest.config.mjs
+```
+
 ## Common Patterns
 ```typescript
 // Async testing