Allow users to register themselves as volunteers ("candidates")

app/controllers/candidates_controller.rb

app/javascript/controllers/bothhands_controller.js

app/models/candidate.rb

app/models/session.rb

app/models/user.rb

app/views/candidates/_user_avatar.html.erb

app/views/sessions/_session.html.erb

config/routes.rb

db/migrate/20241118161733_create_candidates.rb

db/schema.rb

test/fixtures/candidates.yml

test/models/candidate_test.rb