Align search URLs with upstream sites

[hqhq1025]

Summary

Makes known search URL shapes realistic while keeping old /search?q=... routes as compatibility aliases.

Canonical search URLs added/emitted:

• Amazon: /s?k=<query> with /search?q=<query> kept as legacy alias.
• Booking: /searchresults.html?ss=<query> with /search?q=<query> kept as legacy alias.
• Google Maps: /maps/search/<query> with /search?q=<query> kept as legacy alias.
• ESPN: /search/_/q/<query> with /search?q=<query> kept as legacy alias.
• Apple: /search/<query> with /search?q=<query> kept as legacy alias.
• Coursera: /search?query=<query> with /search?q=<query> kept as legacy alias.
• Hugging Face: /search/full-text?q=<query> with /search?q=<query> kept as legacy alias.
• Cambridge Dictionary: /search/direct/?datasetsearch=english&q=<query> with /search?q=<query> kept as legacy alias.
• Cambridge Thesaurus: /search/english-thesaurus/direct/?datasetsearch=english-thesaurus&q=<query> with /thesaurus?q=<query> kept as legacy alias.

Audited and documented as already close to upstream shape or intentionally different:

• Google Search: /search?q=<query> plus vertical params such as tbm=....
• GitHub: /search?q=<query>&type=....
• BBC: /search?q=<query>.
• arXiv: /search/?query=<query>&searchtype=....
• WolframAlpha: /input?i=<query> for computation and /search?q=... for topic search.
• Google Flights: primary flight searches already use /flights?...; generic /search?q=... is a local airport/city/airline helper.

For path-based search URLs, small submit handlers rewrite the destination before navigation so the browser location becomes the upstream-shaped URL. Existing no-JS/query-string aliases still resolve through the same search view.

Also adds:

• docs/search-url-realism.md
• scripts/check_search_url_realism.py

Verification

• python3 scripts/check_search_url_realism.py
• python3 -m py_compile sites/amazon/app.py sites/booking/app.py sites/google_map/app.py sites/espn/app.py sites/apple/app.py sites/coursera/app.py sites/huggingface/app.py sites/cambridge_dictionary/app.py scripts/check_search_url_realism.py
• Flask test-client route checks for canonical and legacy URLs:
  • Amazon /s?k=xbox and /search?q=xbox
  • Booking /searchresults.html?ss=Paris and /search?q=Paris
  • Google Maps /maps/search/central%20park and /search?q=central%20park
  • ESPN /search/_/q/lakers and /search?q=lakers
  • Apple /search/iphone and /search?q=iphone
  • Coursera /search?query=python and /search?q=python
  • Cambridge /search/direct/?datasetsearch=english&q=hello and /search?q=hello
• Hugging Face full route was covered by static regression and py_compile; full render smoke requires HF-managed image assets that are not present in this isolated worktree.

Fixes #14.