feat: Encryption Package Implementation

[AnonO6]

Description

This PR introduces new cryptographic key management functionality under the Kavach class to the SDK, implementing Shamir's Secret Sharing for secure key distribution and recovery.
This PR solves the following issues: #27 and #25

New Features:

1. Key Generation

• Implements secure generation of master keys using cryptographically secure random numbers
• Creates key shards using polynomial evaluation over a finite field
• Supports configurable threshold and total number of shares

2. Key Recovery

• Implements Lagrange interpolation for reconstructing the master key from shares
• Handles various edge cases and invalid inputs gracefully
• Includes comprehensive input validation
• Supports recovery with any number of valid shares

3. Configuration

• Defines `prime modulus' parameter.

Technical Details:

• Uses Python's secrets module for cryptographically secure random number generation
• Implements finite field arithmetic for polynomial operations
• Includes comprehensive error handling and input validation
• Didn't used python's secretsharing package (suggested in the issue) as it is deprecated for python3.
• Prime modulus Value is set to 2**256 + 297 to handle 32 byte keys.

Testing:

• Unit tests cover all major functionality
• Test cases include:
• Basic key generation and recovery
• Edge cases (empty input, invalid shares)
• Various combinations of shares
• Api follows the same structure as JS SDK

Refrences:

https://en.wikipedia.org/wiki/Shamir%27s_secret_sharing