fix(session): restore sidebar creation actions and centered search

[xiami762]

Summary

• restore create-session actions on the Tasks and project rows
• keep row actions hover-driven and place the project create action after the actions menu
• move task search into a centered command-style dialog
• show the five most recently updated sessions before a query is entered
• add interaction coverage and localized search labels

Testing

• npm run test:run -- src/pages/Session/index.test.tsx src/i18n.test.ts
• npm run lint -- --quiet
• npm run build