fix: improve feature card readability and contrast (#319)

[Jai-Shankar1033]

Summary

Improves the readability and accessibility of feature cards on the landing page.
Fixes low text contrast, conflicting CSS rules, and light/dark theme inconsistencies.
Closes #319

---

Type of Change

• Bug fix
• UI / Design change

---

What Changed

• Removed glass class from all 3 feature cards (was breaking light mode display)
• Removed 4 duplicate/conflicting .feature-card CSS rules
• Added explicit color: var(--text-primary) on .feature-card h3 for reliable heading contrast
• Added background 0.35s ease to transition for smooth theme switching
• Dark mode body text upgraded to #e2e8f0 (~11:1 contrast ratio ✅ WCAG AAA)
• Enhanced dark mode border visibility rgba(255,255,255,0.18)
• Smooth hover effect: translateY(-6px) + indigo glow shadow in both themes
• Removed duplicate @media (max-width: 640px) block

---

How to Test

1. Run cd apps/web && pnpm dev and open http://localhost:5173
2. Scroll to feature cards — verify text is clearly readable in dark mode
3. Click the theme toggle button — verify cards display correctly in light mode
4. Hover over cards — verify smooth lift + indigo border glow animation

---

Checklist

• My code follows the project's coding style (pnpm -r run lint passes).
• TypeScript compiles without errors (pnpm -r run typecheck).
• I have added or updated tests for the changes I made.
• All tests pass locally (pnpm -r run test).
• I have updated documentation where necessary.
• No new console.log or debug statements left in the code.
• Breaking changes are documented in this PR description.

---

Screenshots / Recordings

---

Additional Context

Feature cards previously had hardcoded dark backgrounds that ignored the light theme and 4 conflicting CSS rules causing unpredictable rendering. All contrast ratios now meet WCAG AA or AAA standards in both themes.