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/help/faq.md

@@ -591,7 +591,7 @@ Short answer: follow the Linux guide, then run the onboarding wizard.
 
 Any Linux VPS works. Install on the server, then use SSH/Tailscale to reach the Gateway.
 
-Guides: [exe.dev](/platforms/exe-dev), [Hetzner](/platforms/hetzner), [Fly.io](/platforms/fly).
+Guides: [exe.dev](/install/exe-dev), [Hetzner](/install/hetzner), [Fly.io](/install/fly).
 Remote access: [Gateway remote](/gateway/remote).
 
 ### Where are the cloudVPS install guides
@@ -599,9 +599,9 @@ Remote access: [Gateway remote](/gateway/remote).
 We keep a **hosting hub** with the common providers. Pick one and follow the guide:
 
 - [VPS hosting](/vps) (all providers in one place)
-- [Fly.io](/platforms/fly)
-- [Hetzner](/platforms/hetzner)
-- [exe.dev](/platforms/exe-dev)
+- [Fly.io](/install/fly)
+- [Hetzner](/install/hetzner)
+- [exe.dev](/install/exe-dev)
 
 How it works in the cloud: the **Gateway runs on the server**, and you access it
 from your laptop/phone via the Control UI (or Tailscale/SSH). Your state + workspace
@@ -910,7 +910,7 @@ Baseline guidance:
 
 If you are on Windows, **WSL2 is the easiest VM style setup** and has the best tooling
 compatibility. See [Windows](/platforms/windows), [VPS hosting](/vps).
-If you are running macOS in a VM, see [macOS VM](/platforms/macos-vm).
+If you are running macOS in a VM, see [macOS VM](/install/macos-vm).
 
 ## What is OpenClaw?