feat: Implement public view system

[hexawulf]

This commit introduces a public view system, allowing unauthenticated users to browse and discover public code snippets.

Key changes include:

• Public Landing Page (PublicHome.tsx): A new page at the root (/) for unauthenticated users, featuring a grid of public snippets, search, and language filtering.
• Public API Endpoints (server/routes.ts):
  • GET /api/public/snippets: Serves all snippets marked as public, with support for search and filtering.
  • GET /api/public/snippets/:id: Serves a single public snippet by ID.
    These endpoints do not require authentication.
• Storage Layer Updates (server/storage.ts):
  • getSnippets method in MemStorage and DatabaseStorage now supports an isPublic filter.
  • Sample data in MemStorage updated to include public/private snippets.
• Authentication-Aware Components:
  • App.tsx: Main router now directs unauthenticated users to PublicHome and authenticated users to their dashboard. Shared snippet routes are accessible in both contexts.
  • Layout.tsx: Accepts an isPublicView prop to render a simplified layout (no sidebar) for public views.
  • SnippetCard.tsx: Accepts isPublicView and uses AuthContext to conditionally display action buttons (Edit, Delete, Favorite, etc.) based on ownership and view context. A "Public" badge is shown for public snippets.
  • SnippetGrid.tsx: Accepts isPublicView, passes it to SnippetCard, and customizes the empty state message.
• Schema (shared/schema.ts): Confirmed userId and isPublic fields are present.
• Testing:
  • Unit test structures created for server/storage.ts (isPublic filter), client/src/components/SnippetCard.tsx (conditional rendering), and server/routes.ts (public API endpoints).
  • An INTEGRATION_TESTS.md file was created outlining integration tests for PublicHome.tsx and routing behavior.

This implementation allows CodePatchwork to serve a broader audience by making public snippets accessible without requiring user login, while maintaining security for private snippets and full functionality for authenticated users.