fix (#903): improve error handling for missing parameters in WalletApiRoute

[dimension-drifter]

###Root Cause
The password directive in [WalletApiRoute.scala] uses a bare reject without providing specific error information when JSON parsing fails.
This causes Akka HTTP to generate a generic "Tag mismatch!" error message instead of a meaningful one.

###Solution
Updated the password directive (and other similar directives) to provide meaningful rejection messages.

###Changes Made
File: [WalletApiRoute.scala]
Fixed the following directives to provide meaningful error messages:

• password - Used by /wallet/unlock endpoint
• derivationPath - Used by /wallet/deriveKey endpoint
• checkRequest - Used by /wallet/check endpoint
• initRequest - Used by /wallet/init endpoint

File: [WalletApiRouteSpec.scala]
Added test cases to verify proper error messages:

• Test /wallet/unlock with missing pass field
• Test /wallet/unlock with empty JSON body
• Test /wallet/deriveKey with missing derivationPath field