[QA] Add Cypress coverage for Tax Connector on stripe

## Description Add Cypress E2E test coverage for the Tax Connector business profile flag feature on the Stripe connector. Tax Connector is a business profile-level flag (`is_tax_connector_enabled`) that enables internal tax calculation during payment creation. Tests validate: 1. Business profile with `is_tax_connector_enabled: true` triggers tax calculation 2. Payment creation with tax calculation triggered 3. `skip_external_tax_calculation` bypass flag works correctly 4. Profile retrieve returns tax fields correctly 5. Tax connector toggle (enable/disable) behavior ## Coverage Details - **New spec:** `cypress/e2e/spec/Payment/54-TaxConnector.cy.js` — 20 tests covering tax enabled, tax disabled, skip flag, profile retrieve, and toggle scenarios - **Config changes:** `cypress/e2e/configs/Payment/Stripe.js` — fixed card metadata fields to null (matches live Stripe API) - **Utils:** `cypress/e2e/configs/Payment/Utils.js` — added TAX_CONNECTOR to CONNECTOR_LISTS.INCLUDE - **Commands:** `cypress/e2e/spec/Payment/commands.js` — added custom commands for business profile tax operations ## Regression Results Full regression against Stripe connector — 20/20 tests passed. ``` RUNNER_RESULT: Connector: stripe SpecFile: cypress/e2e/spec/Payment/54-TaxConnector.cy.js PrereqsUsed: spec/Payment/01-AccountCreate, 02-CustomerCreate, 03-ConnectorCreate TotalTests: 20 Passed: 20 Failed: 0 Skipped: 0 OverallStatus: PASS ``` ## Related - Paperclip issue: SPI-128 — Tax Connector Feature