docs: link the shared privacy policy from the footer

[hannesrudolph]

What Problem This Solves

Adds a discoverable link to the shared website privacy policy from the docs footer.

User Impact

Readers find Privacy policy in the existing Resources group, linking to https://openclaw.ai/privacy with the standard footer styling and navigation behavior.

Why This Change Was Made

The shared policy is intended to cover all five sites. This draft depends on the policy-coverage changes in openclaw/openclaw.ai#396 before merge.

The change adds only the link and its existing footer smoke assertion. Policy copy, layout, analytics/consent behavior, repository variables and deployment workflows are unchanged.

Evidence

• npm test: 274 passed; one optional SDK test skipped.
• Bounded preview: 30 pages including Getting Started.
• Desktop (1440×900) and mobile (390×844): exactly one link under Resources, correct href, keyboard focus, unobscured placement and no horizontal overflow. External requests were blocked during local rendering.
• Structured Autoreview: clean, no actionable findings.
• Vercel inventory: no Analytics/Speed Insights package, loader, endpoint or shim in renderer/workers, manifest/lockfile, installed dependency tree or generated preview. No removal was needed; GA4 and hosting remain unchanged.

This remains a draft pending the shared policy dependency; no merge or deployment is included.