migrate hello-privy example from JSX to TSX

[Amira1502]

PR Description

This PR translates the hello privy example from JavaScript to TypeScript.

Changes:

• Converted all React components and context files to .tsx for proper typing.
• Added explicit types for:
  • PrivySigner class (typed with SignRawHashParams, SignRawHashOutput, SignRawHashFn)
  • NEARxPrivy provider props and context value
  • user, walletId, and nearAccount states
• Introduced template literal types (e.g. 0x${string} for raw hash values).
• Updated tsconfig.json