Complete initial setup: dependencies, Prisma fixes, and database setup guides

- Install backend and frontend dependencies
- Fix Prisma schema BigInt default values
- Generate Prisma client
- Create database setup script and documentation
- Add DATABASE_SETUP.md guide

backend/prisma/schema.prisma

@@ -187,8 +187,8 @@ model ChainConfig {
   name              String
   nativeToken       String?
   explorerUrl       String
-  gasLimit          BigInt   @default("3000000")
-  messageTimeout    BigInt   @default("300") // seconds
+  gasLimit          BigInt   @default(3000000)
+  messageTimeout    BigInt   @default(300) // seconds
   active            Boolean  @default(true)
   ccipSelector      BigInt?
   rpcUrl            String?