Plans by goal and an editor theme that sticks

What changed

• The Plans page lists plans by goal: Big Tech Interview, Data Analyst, and Startup & AI-Assisted.
• The editor theme menu adds Match site, which follows the site's light and dark toggle. A theme you pick stays on that device through reloads.
• Builder projects get the whole screen, with an X back to your projects. Lessons no longer spend two Rena hints on one missed run.