fix(studio): extend generated project timeout

[xgtcode]

Summary

• Extend generateAgentProject() timeout for POST /web/generated-agent-projects from the default 30s to a dedicated 60s deadline.
• Add a specific timeout error message for publish preview project generation instead of surfacing the generic aborted request error.
• Add regression coverage for the dedicated generated project timeout and timeout error handling.
• Rebuild and include updated veadk/webui packaged assets.

Verification

• npm --prefix frontend run build
• npm --prefix frontend run check:i18n
• npm --prefix frontend test
• npm --prefix frontend run test:webui-assets
• uv run pre-commit run --files <staged files>