feat: add fullstack app-type and --message to apps +create

[raistlin042]

Summary

Add a fullstack app type to apps +create alongside the existing HTML. When --app-type fullstack, a new --message flag is required and forwarded verbatim in the create request body so the server can generate the app from the user's description. For HTML, --message is silently ignored. The lark-apps skill now routes between HTML and fullstack based on the user's intent.

Changes

• Add fullstack to the app-type allow-list and a new --message flag in shortcuts/apps/apps_create.go; conditional validation (fullstack requires non-blank message) and request-body injection of message only for fullstack.
• Add unit tests in shortcuts/apps/apps_create_test.go: fullstack success, required/blank message rejection, HTML message-ignore, dry-run, and case-sensitive rejection.
• Document HTML vs fullstack intent routing, --message, the fullstack scenario, and skill description trigger words in skills/lark-apps/SKILL.md and skills/lark-apps/references/lark-apps-create.md.

Test Plan

• make unit-test passed (./shortcuts/apps/ green)
• validate passed (build / vet / unit / integration)
• local-eval passed (E2E 4/4 dry-run, skillave 5/5)
• acceptance-reviewer passed (9/9 cases)
• manual verification: lark-cli apps +create --name "团队任务看板" --app-type fullstack --message "带登录和数据库的任务看板" --dry-run --as user — request body carries app_type: fullstack and message; missing message exits 2
• skipped: real backend round-trip — the server-side fullstack interface is not deployed yet and the request-body field name (message) is tentative; real create verification is deferred until the backend ships

Related Issues

N/A