docs: restructure Get Started tab and improve onboarding flow (#9950)

* docs: restructure Get Started tab and improve onboarding flow

- Flatten nested Onboarding group into linear First Steps flow
- Add 'What is OpenClaw?' narrative section to landing page
- Split wizard.md into streamlined overview + full reference (reference/wizard.md)
- Move Pairing to Channels > Configuration
- Move Bootstrapping to Agents > Fundamentals
- Move macOS app onboarding to Platforms > macOS companion app
- Move Lore to Help > Community
- Remove duplicate install instructions from openclaw.md
- Mirror navigation changes in zh-CN tabs
- No content deleted — all detail preserved or relocated

* docs: move deployment pages to install/, fix Platforms tab routing, clarify onboarding paths

- Move deployment guides (fly, hetzner, gcp, macos-vm, exe-dev, railway, render,
  northflank) from platforms/ and root to install/
- Add 'Hosting and deployment' group to Install tab
- Slim Gateway & Ops 'Remote access and deployment' down to 'Remote access'
- Swap Platforms tab before Gateway & Ops to fix path-prefix routing
- Move macOS app onboarding into First steps (parallel to CLI wizard)
- Rename sidebar titles to 'Onboarding: CLI' / 'Onboarding: macOS App'
- Add redirects for all moved paths
- Update all internal links (en + zh-CN)
- Fix img tag syntax in onboarding.md

docs/zh-CN/vps.md

@@ -22,10 +22,10 @@ x-i18n:
 - **Railway**（一键 + 浏览器设置）：[Railway](/railway)
 - **Northflank**（一键 + 浏览器设置）：[Northflank](/northflank)
 - **Oracle Cloud（永久免费）**：[Oracle](/platforms/oracle) — $0/月（永久免费，ARM；容量/注册可能不太稳定）
-- **Fly.io**：[Fly.io](/platforms/fly)
-- **Hetzner（Docker）**：[Hetzner](/platforms/hetzner)
-- **GCP（Compute Engine）**：[GCP](/platforms/gcp)
-- **exe.dev**（VM + HTTPS 代理）：[exe.dev](/platforms/exe-dev)
+- **Fly.io**：[Fly.io](/install/fly)
+- **Hetzner（Docker）**：[Hetzner](/install/hetzner)
+- **GCP（Compute Engine）**：[GCP](/install/gcp)
+- **exe.dev**（VM + HTTPS 代理）：[exe.dev](/install/exe-dev)
 - **AWS（EC2/Lightsail/免费套餐）**：也运行良好。视频指南：
   https://x.com/techfrenAJ/status/2014934471095812547