feat: add end user delegated signing API to Java and Python SDKs

[sammccord]

Description

Adds delegated signing and sending support for end users across the Java and Python SDKs, including examples and documentation.

Python SDK

• Wired EmbeddedWalletsCoreFunctionalityApi into ApiClients
• Added get_end_user and 15 delegated signing/sending methods to EndUserClient (sign/send EVM hash, message, transaction, typed data, asset, user operation; sign/send Solana hash, message, transaction, asset; EIP-7702 delegation; revoke delegation)
• Added corresponding action methods to EndUserAccount with auto-bound userId and defaulted address
• Updated CdpClient to read CDP_PROJECT_ID and pass project_id through to EndUserClient and EndUserAccount
• Updated _requires_wallet_auth() to include /embedded-wallet-api/ paths
• Updated python/README.md with documentation for all new end-user operations

Java SDK

• Updated OpenAPI-generated models and APIs for delegated signing endpoints
• Added EndUserClient with projectId configuration and all delegated signing/sending methods
• Updated CdpClient and CdpClientOptions to support projectId

Examples

• Created 16 Java end-user example files with Gradle tasks
• Created 8 Python end-user example files
• Updated TypeScript examples/typescript/README.md with comprehensive end-user sections

Checklist

• Updated the python README if relevant
• Updated the typescript README if relevant
• Added a changelog entry
• Added e2e tests if introducing new functionality

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[github-actions]

⚠️ Generated Client Files Have Been Modified

This pull request contains manual changes to generated client files. These files are automatically generated from the OpenAPI specification and should not be edited directly.

Please check the workflow logs for details on which files were modified.

To fix this issue:

1. Revert any manual changes to files in:
   • typescript/src/openapi-client/generated/
   • python/cdp/openapi_client/
   • go/openapi/
   • java/src/main/java/com/coinbase/cdp/openapi/
2. If you need to change the generated code, update the OpenAPI spec (openapi.yaml) instead
3. Run the generation commands locally to update the generated files

_{This comment will be automatically removed once the issue is resolved.}