feat(studio): add BytePlus provider support

[richarddancin]

Summary

• add a Studio cloud provider switch for BytePlus, including BytePlus branding, ap-southeast-1 defaults, and provider-specific cloud endpoints
• route AgentKit Studio runtime, skill/A2A/knowledge, VeFaaS, APIG, CP, Identity, VikingDB, and ModelArk flows through BytePlus when --provider byteplus is selected
• merge AgentKit-imported Viking knowledge bases into Studio selection and keep provider-specific UI dropdowns unclipped

Tests

• UV_CACHE_DIR=/tmp/uv-cache PYTHONPYCACHEPREFIX=/tmp/veadk-pycache uv run pytest tests/cli/test_studio_deploy_target.py tests/test_cloud.py tests/cli/test_frontend_runtime_proxy.py::test_viking_knowledgebases_include_agentkit_imported_bases tests/test_vikingdb_knowledge_backend.py -q
• npm test -- --runInBand
• npm run build
• git diff --check
• git diff --cached --check -- . ':(exclude)veadk/webui/assets/*.js'