feat(frontend): add dark mode with theme toggle and localStorage pers…

[oncleweynom]

What
Adds manual dark mode support to the app — a toggle button in the navbar lets users switch between light and dark themes, with their preference saved across sessions.

Why
The codebase already had dark: Tailwind classes in place but no mechanism to activate them. Dark mode was purely driven by the OS setting with no user control. This completes the implementation.

Changes
globals.css
— migrated dark mode from prefers-color-scheme media query to .dark class strategy using Tailwind v4's @variant
layout.tsx
— added a synchronous inline script that reads localStorage and applies .dark before React hydrates, eliminating flash of wrong theme. Added suppressHydrationWarning on
ThemeToggle.tsx
— icon button (sun/moon) that reads from and writes to the theme store
Navbar.tsx
— mounts ThemeToggle between the Pools link and ConnectWallet
themeStore.ts
— Zustand store managing theme, setTheme, and toggleTheme. Writes to localStorage on every change
index.ts
— exports useThemeStore and Theme type
index.ts
— exports ThemeToggle
Behaviour
First visit: checks localStorage first, falls back to prefers-color-scheme
Toggle: switches theme instantly, persists choice to localStorage
No flash: inline script runs before paint, before hydration
All existing dark: classes across the app activate automatically — no page-level changes needed
Build
next build --webpack passes clean ✓
ESLint + Prettier pre-commit hooks pass ✓

close #430

[drips-wave]

@oncleweynom Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits