Set up web E2E tests and cover current functionality

## Summary
Set up end-to-end tests for the web experience and cover the current user-facing functionality.

## Scope
- Choose and configure an E2E test runner for the web frontend, preferably Playwright unless there is a stronger project reason to use something else.
- Add E2E coverage for current public pages and admin flows.
- Include country homepage routing, product/article listing pages, detail pages, admin login/register, and admin CRUD flows where practical.
- Document how to run E2E tests locally and in CI.

## Acceptance Criteria
- E2E test tooling is installed and documented.
- Current public web functionality has baseline E2E coverage.
- Current admin functionality has baseline E2E coverage.
- Tests can run against a local test environment with deterministic data.
- CI can run the E2E suite or has a clearly documented follow-up for enabling it.

Start by identifying the web frontend's public routes, admin login/register flows, CRUD entry points, and local test environment. Configure Playwright, add baseline coverage for the listed public and admin functionality using deterministic data, document local and CI execution, and verify the acceptance criteria.

Written by the indexing model from the issue text.