Add functional end-to-end tests for the paste create/view/raw flows (Playwright, zero setup)

[qosha1]

What this adds

8 passing functional end-to-end tests (Playwright) covering microbin:

• Create & view a paste — fill the upload form and submit, then follow the redirect to the paste permalink and assert the content is rendered back.
• Create after visiting a paste permalink — load a paste permalink first, then create and view a paste.
• Create from the paste list — open the /list view, then create and view a paste.
• Create from the guide page — open the /guide page, then create and view a paste.
• Create via list -> guide — visit the list then the guide, then create and view a paste.
• Create via guide -> list — visit the guide then the list, then create and view a paste.
• Create after the remove route — hit the /remove/{id} route, then create and view a paste.
• Create after the edit route — hit the /edit/{id} route, then create and view a paste.

_{Generated with the help of debugg.ai, then reviewed and run locally before opening. Happy to adjust or drop these if you'd rather not carry them — just say the word.}

Coverage summary

#	Flow
1	Create & view a paste
2	Create after visiting a paste permalink
3	Create from the paste list
4	Create from the guide page
5	Create via list -> guide
6	Create via guide -> list
7	Create after the remove route
8	Create after the edit route

All 8 tests pass green on a clean checkout — 0 skipped, 0 flaky.

How to run

Standalone Playwright tests under e2e/. They reach the app over HTTP via a configurable BASE_URL.

# start the app, then from e2e/ :
npm install
npx playwright install chromium
BASE_URL=http://localhost:8080 npx playwright test