Refine user settings menu and access shortcuts

[lyingbug]

Summary

• refocus the avatar menu on account and workspace actions
• move web search, MCP, and API integration shortcuts into All Settings
• show member and model management shortcuts only to users with matching write access
• rename the privileged entry to System Administration and add a documentation link
• centralize frontend settings access policies and cover shortcut thresholds with tests
• add localized labels for all supported locales

Why

The avatar menu had accumulated an arbitrary subset of infrastructure settings while omitting peer settings, making it both long and incomplete. It also exposed management-labelled shortcuts to read-only users. This change gives the menu a clearer account/workspace purpose while preserving the complete settings navigation as the source of truth.

User impact

Users get direct Personal Settings and Workspace Settings entries. Owners and administrators retain relevant management shortcuts, while read-only users can still browse the corresponding pages through All Settings. System administrators keep a dedicated entry for the full administration group.

Validation

• npm run build-only
• npx tsx --test src/config/settingsAccess.test.ts
• supported-locale key presence check for Chinese, English, Russian, and Korean
• git diff --check

Known baseline issues outside this diff:

• npm run type-check reports existing errors in sessionSidebarBuckets.ts, AgentEditorModal.vue, and SystemSettings.vue
• npm test passes 246 tests and retains 2 existing workspace-terminology failures in unrelated locale/docs content