refactor: replace manual state with computed property, unify client selection

docs: bigger logo, tighter spacing below badges

docs: add SVG logo to hero, move dashboard back to screenshots

docs: fact-check README, add hero image, remove competitor table

docs: add competitive comparison and highlight unique features

docs: rewrite README with screenshots, features, and architecture

fix: prevent silent deep research → pro downgrade

fix: replace assert with ValidationError in Client.search()

fix: handle None response from search() on dropped connection

fix: move blocking HTTP calls outside pool lock in get_user_info methods

fix: rotation loop no longer skips clients + regex error classification

fix: replace mutable default arguments with None

fix: make _save_config atomic and stop calling it on every request

docs: add bugfix audit implementation plan

fix: _save_config uses _cookies instead of session jar