Reorganize repository into monorepo structure

Restructured the project to support multiple frontend applications:
- Move web app to web/ directory
- Create pezkuwi-sdk-ui/ for Polkadot SDK clone (planned)
- Create mobile/ directory for mobile app development
- Add shared/ directory with common utilities, types, and blockchain code
- Update README.md with comprehensive documentation
- Remove obsolete DKSweb/ directory

This monorepo structure enables better code sharing and organized
development across web, mobile, and SDK UI projects.

shared/utils/validation.ts

@@ -0,0 +1,28 @@
+/**
+ * Validation utilities
+ */
+
+/**
+ * Validate if a string is a valid blockchain address
+ * @param address - Address to validate
+ * @returns True if valid, false otherwise
+ */
+export function isValidAddress(address: string): boolean {
+  // Basic validation - extend based on your blockchain requirements
+  if (!address) return false;
+
+  // Substrate/Polkadot addresses typically start with specific characters
+  // and have a specific length
+  return address.length >= 47 && address.length <= 48;
+}
+
+/**
+ * Validate if a string is a valid amount
+ * @param amount - Amount to validate
+ * @returns True if valid, false otherwise
+ */
+export function isValidAmount(amount: string): boolean {
+  if (!amount) return false;
+  const num = parseFloat(amount);
+  return !isNaN(num) && num > 0;
+}