feat: Add support for 24-word mnemonic phrases and fix API headers

[naveenkumar29052006]

Summary

This PR adds support for importing wallets using 24-word mnemonic phrases (in addition to the existing 12-word support) and fixes missing Content-Type headers in API requests that were causing 400 Bad Request errors.

Changes

1. 24-Word Mnemonic Support (ImportWallet.tsx)

• Added a radio button selector to choose between 12-word and 24-word mnemonic phrases
• Added phraseLength field to form state to track the selected phrase length
• Updated mnemonic validation to properly validate variable-length phrases
• Improved dummy mnemonic generation to work with both 12 and 24-word phrases
• Added wallettype: 'sw-fb' parameter to the wallet recovery API call

2. API Header Fixes (JmWalletApi.ts)

• Added missing Content-Type: application/json headers to all POST requests:
  • /v1/token
  • /v1/wallet/create
  • /v1/wallet/recover
  • /v1/wallet/{walletFileName}/unlock
  • /v1/wallet/{walletFileName}/maker/start
  • /v1/wallet/{walletFileName}/taker/direct-send
  • /v1/wallet/{walletFileName}/taker/coinjoin
  • /v1/wallet/{walletFileName}/freeze
  • /v1/wallet/{walletFileName}/taker/schedule
  • /v1/wallet/{walletFileName}/configset
  • /v1/wallet/{walletFileName}/configget

Motivation

• 24-word support: BIP39 standard supports both 12 and 24-word mnemonic phrases. Users with 24-word phrases were unable to import their wallets.
• API headers: The JoinMarket API expects Content-Type: application/json headers for POST requests with JSON bodies. Missing headers were causing 400 Bad Request errors during wallet operations.

Testing

• [x] Manually tested importing wallet with 12-word mnemonic phrase
• [x] Manually tested importing wallet with 24-word mnemonic phrase
• [x] Verified API requests now include proper Content-Type headers
• [x] Code formatted with Prettier (pre-commit hook)