Add Versus mirror site

[Sun-sunshine06]

Summary

• Adds a Versus mirror under sites/versus with product categories, rankings, search, detail pages, side-by-side comparisons, saved comparisons, and benchmark users.
• Covers smartphones, headphones, cameras, graphics cards, and smartwatches with 20 seeded products and specification-aware search.
• Registers versus in websyn_start.sh and control_server.py as the next site, exposed on port 40036.
• Adds Docker build-time seed generation for the code-generated SQLite seed DB.

Verification

• sites/versus/venv/Scripts/python.exe -m py_compile sites/versus/app.py
• python -m py_compile control_server.py
• tasks.jsonl JSON parse check passed
• Flask test client smoke: /, /categories, /category/smartphones, /item/iphone-15-pro, /compare, /compare/iphone-15-pro-vs-samsung-galaxy-s24-ultra, /rankings, /search?q=sony+headphones, /login all returned 200
• Login as alice.j@test.com and save comparison flow returned 200
• Spec search smoke: 40 megapixels camera, 50 hours battery headphones, graphics cards 24GB returned matching pages
• Local seed byte-identity check: instance/versus.db matched instance_seed/versus.db after a second import

Note

• This PR is independent from the AKC PR. If AKC is merged first, this branch should be rebased so Versus moves to the next port.

[Sun-sunshine06]

Moved this PR to the upstream aiming-lab/WebHarbor repo: aiming-lab#41