Implement comprehensive error handling

- Add try-catch blocks to all server actions with retry logic
- Implement exponential backoff retry mechanism for database operations
- Add input validation to all server actions
- Create ErrorBoundary component for React error handling
- Add page-level error handlers (error.tsx, global-error.tsx)
- Add route-specific error pages for list and item routes
- Enhance database connection with graceful error handling
- Add user-friendly error messages throughout the application
- Implement proper error logging for debugging

Task: 16. Implement error handling
Requirements: All (error handling is cross-cutting)

lib/db.ts

@@ -4,6 +4,22 @@ const globalForPrisma = globalThis as unknown as {
   prisma: PrismaClient | undefined
 }
 
-export const prisma = globalForPrisma.prisma ?? new PrismaClient()
+// Create Prisma client with connection error handling
+export const prisma = globalForPrisma.prisma ?? new PrismaClient({
+  log: process.env.NODE_ENV === 'development' ? ['error', 'warn'] : ['error'],
+})
+
+// Handle connection errors
+prisma.$connect().catch((error) => {
+  console.error('Failed to connect to database:', error)
+  // Don't throw here - let individual queries handle connection errors
+})
+
+// Graceful shutdown
+if (typeof window === 'undefined') {
+  process.on('beforeExit', async () => {
+    await prisma.$disconnect()
+  })
+}
 
 if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma