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/help/faq.md

@@ -572,7 +572,7 @@ curl -fsSL https://openclaw.ai/install.sh | bash -s -- --install-method git
 
 任何 Linux VPS 都可以。在服务器上安装，然后使用 SSH/Tailscale 访问 Gateway 网关。
 
-指南：[exe.dev](/platforms/exe-dev)、[Hetzner](/platforms/hetzner)、[Fly.io](/platforms/fly)。
+指南：[exe.dev](/install/exe-dev)、[Hetzner](/install/hetzner)、[Fly.io](/install/fly)。
 远程访问：[Gateway 网关远程](/gateway/remote)。
 
 ### 云/VPS 安装指南在哪里
@@ -580,9 +580,9 @@ curl -fsSL https://openclaw.ai/install.sh | bash -s -- --install-method git
 我们维护了一个**托管中心**，涵盖常见提供商。选择一个并按指南操作：
 
 - [VPS 托管](/vps)（所有提供商汇总）
-- [Fly.io](/platforms/fly)
-- [Hetzner](/platforms/hetzner)
-- [exe.dev](/platforms/exe-dev)
+- [Fly.io](/install/fly)
+- [Hetzner](/install/hetzner)
+- [exe.dev](/install/exe-dev)
 
 在云端的工作方式：**Gateway 网关运行在服务器上**，你通过控制 UI（或 Tailscale/SSH）从笔记本/手机访问。你的状态 + 工作区位于服务器上，因此将主机视为数据来源并做好备份。
 
@@ -863,7 +863,7 @@ OpenClaw 是轻量级的。对于基本的 Gateway 网关 + 一个聊天渠道
 - **操作系统：** Ubuntu LTS 或其他现代 Debian/Ubuntu。
 
 如果你使用 Windows，**WSL2 是最简单的虚拟机式设置**，具有最佳的工具兼容性。参阅 [Windows](/platforms/windows)、[VPS 托管](/vps)。
-如果你在虚拟机中运行 macOS，参阅 [macOS VM](/platforms/macos-vm)。
+如果你在虚拟机中运行 macOS，参阅 [macOS VM](/install/macos-vm)。
 
 ## 什么是 OpenClaw？