Add copy note link action to sidebar context menus

[Isjuanplayer]

Fixes #313.

Summary

• Add a Copy the link action to document context menus in the cloud sidebar.
• Add the same action to the mobile navigator tree so copied note links are available consistently.
• Use the existing absolute document href and copy-to-clipboard, matching the app's existing copy-link behavior in document metadata/actions.
• Keep rename/delete restricted to core members while allowing copy-link for non-core users too.

Validation

• npx tsc --noEmit --pretty false
• npx prettier --check "src/cloud/lib/hooks/sidebar/useCloudSidebarTree.tsx" "src/mobile/lib/sidebar/useNavigatorTree.tsx"
• npx eslint "src/cloud/lib/hooks/sidebar/useCloudSidebarTree.tsx" "src/mobile/lib/sidebar/useNavigatorTree.tsx"
• git diff --check

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