FAQ — landing page (support/faq/index)

**Page:** `support/faq/index.mdx`

**Context:** Siblings `getting-started`, `hbar`, `governance`, `community` are written.

**Scope:** FAQ landing routing into the category pages; optionally a top-questions list.

### Acceptance criteria
- [ ] Replace the placeholder template with a real landing page
- [ ] Remove `hidden: true` from the frontmatter
- [ ] **No "Browse by section" block** — the side nav covers that; open straight into the deep-dive sections
- [ ] Route into the written sibling pages via ``/``
- [ ] Follow the style guide (markdown tables only; no AI-tell phrasing)