fix(web): match verify-email Synvya branding to client app

[alejandro-runner]

Summary

• Replace the Keycast "divine" green theme on the Synvya-managed verify-email page with the Synvya client app's design tokens
• Add prefers-color-scheme support so the page respects system light/dark mode (white background in light, dark slate in dark)
• Update buttons from dark pills (#0f172a, border-radius: 9999px) to green rounded buttons matching the client (hsl(142.1 76.2% 36.3%), 0.375rem)
• Fix text colors, icon chip backgrounds, and font stack for both modes
• Update page title to "Verify Email - Synvya Restaurant"

All changes are scoped to .synvya-* CSS selectors — the generic Keycast divine theme is untouched.

Test plan

• Deploy to staging and open auth.staging.synvya.com/verify-email (no-token state)
• Verify light mode: white background, dark text, green primary button, subtle bordered secondary button
• Verify dark mode: dark slate background (hsl(222.2 84% 4.9%)), light text, same green button
• Confirm the generic Keycast verify-email page (login.divine.video/verify-email) still uses the divine green theme
• Test a real verification flow end-to-end from a Synvya invitation link

🤖 Generated with Claude Code