Subscribe landing /subscribe: creator search not example-only

[aji70]

Context / Why

app/subscribe/page.tsx and subscribe-example. Should search creators and deep-link to confirm. Example page gated in prod (see demo routes issue).

Current state

subscribe/page.tsx. subscribe-example. creators search API.

Proposed work

1. Search UI.
2. Results from API.
3. Empty query state.
4. Auth optional until confirm.
5. Remove example from prod nav.

Acceptance criteria

• Search works.
• Click goes to confirm.
• No example in prod nav.
• Loading/error.
• A11y combobox if used.

Out of scope

Fuzzy search ranking.