fix(settings): fix Tavily key label cursor and reunite the apply link - #3821

Summary

Two small UI papercuts in Settings → Web search's Tavily key field:

• Misleading cursor. The key label ("Tavily 密钥" / "Tavily key") showed a hand (pointer) cursor on hover but forwards no click. Astryx FieldLabel renders an InputGroup label as a bare <span class="astryx-field-label"> (isGroupLabel), which carries StyleX cursor: pointer; native-cursor.css (the single owner of the "hand cursor is for links only" convention) only neutralized real <label> elements, so the span slipped through. Match the stable themeProps class (.astryx-field-label) so group-label spans get cursor: default like every other field label. This is app-wide by design — the same shared PasswordInput backs bot tokens, provider API keys, and the proxy password.
• Apply URL split from its label. "申请地址：" / "Apply at:" rendered above the input as the field description, while the tavily.com link rendered on its own line below the input, so the key input split the label from its URL. Fold the link into the description as a ReactNode so "申请地址：tavily.com" reads as one unit above the input — a pattern Astryx FieldLabel supports (its click forwarding skips nested interactive content); only InputGroup/Field under-declare the description prop as string, papered over by one cast in PasswordInput.

Fixes #3820

Verification

• tsc -p tsconfig.renderer.json --noEmit — passes
• biome lint on the changed files — passes

Before / after (Tavily key field):

Before                               After
─────────────────────────────       ─────────────────────────────
Tavily 密钥        (hand cursor)     Tavily 密钥        (arrow cursor)
密钥只保存在本机。申请地址：           密钥只保存在本机。申请地址：tavily.com
┌───────────────────────────┐        ┌───────────────────────────┐
│ tvly-xxxxxxxx      👁 📋 │          │ tvly-xxxxxxxx      👁 📋 │
└───────────────────────────┘        └───────────────────────────┘
tavily.com   ← split below input

before

after

Review focus

The cursor fix in native-cursor.css is intentionally app-wide: it neutralizes the hand cursor on every InputGroup group-label span, not just this page.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code (Opus 4.8) — investigated the root cause, wrote the code changes, and drafted this PR. Reviewed by the author. The squash commit carries a Generated-by trailer.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No