fix(docs): standardize C4A-Script tutorial, add CLI identity-based crawling, and add sponsorship CTA

- Switch installs to pip install -r requirements.txt (tutorial and app docs)
- Update local run steps to python server.py and http://localhost:8000
- Set default PORT to 8000; update port-in-use commands and alt port 8001
- Replace unsupported :contains() example with accessible attribute selector
- Update example URLs in tutorial servers to 127.0.0.1:8000
- Add “Identity-based crawling” section with crwl profiles CLI workflow and code usage
- Replace legacy-docs note with sponsorship message in docs/md_v2/index.md
- Minor copy and consistency fixes across pages

docs/examples/c4a_script/tutorial/server.py

@@ -216,7 +216,7 @@ def get_examples():
             'name': 'Handle Cookie Banner',
             'description': 'Accept cookies and close newsletter popup',
             'script': '''# Handle cookie banner and newsletter
-GO http://127.0.0.1:8080/playground/
+GO http://127.0.0.1:8000/playground/
 WAIT `body` 2
 IF (EXISTS `.cookie-banner`) THEN CLICK `.accept`
 IF (EXISTS `.newsletter-popup`) THEN CLICK `.close`'''