Switch the primary UI font to Inter

The app-wide UI font is now Inter (was Host Grotesk). Loaded via the existing --font-outfit variable, so all body text, Tailwind sans/display/body tokens, and inline references pick it up with no rename. Space Grotesk and JetBrains Mono are retained for the text-card font picker and the mono timer.

Changed

• app/layout.tsx — imports Inter from next/font/google in place of Host_Grotesk, keeping the --font-outfit variable.
• components/cards/TextCard.tsx — default font option relabeled "Outfit" → "Inter" (the "outfit" id is kept for back-compat with saved cards).
• app/page.tsx — the "Ask AI" button no longer hard-codes Space Grotesk; it uses the primary font (Inter) for consistency.