feat: Frontend Polish - Search, Toasts, and Skeletons

[ViVaLaDaniel]

Summary

This PR implements multiple Tier 1 bounties (#823, #825, #827) to improve the user experience and interface of the SolFoundry platform.

Changes

🔍 Search Functionality (#823)

• Added a real-time, debounced search bar to the /bounties page.
• Users can now filter bounties by title, description, or tags.
• Includes a clear-search button for quick reset.

🍞 Toast Notification System (#825)

• Implemented a global ToastContext and ToastProvider.
• Added a stylish, animated toast notification system with Success, Error, Warning, and Info variants.
• Features auto-dismiss progress bars and manual close support.

💀 Loading Skeletons (#827)

• Added shimmer-effect loading skeletons for bounty cards.
• Integrated skeletons into the BountyGrid loading state for a smoother transition from loading to content.

Technical Details

• Built with TypeScript and Framer Motion for animations.
• Uses Lucide React for icons.
• New hooks: useDebounce, useToast.
• New component: Skeleton.