feat(settings): unified settings modal with context switcher (Phase 1)

New unified settings modal accessible via `,` keyboard shortcut.
Three-context switcher: Site (with site dropdown), Workspace, Account.
Horizontal tabs per context with animated transitions.

Phase 1 tabs implemented:
- Site → General (name, timezone, domain, tracking script with copy)
- Site → Goals (CRUD with inline create/edit)
- Workspace → General (org name, slug, danger zone)
- Workspace → Billing (plan card, usage, cancel/resume, portal)
- Account → Profile (wraps existing ProfileSettings)

Phase 2 tabs show "Coming soon" placeholder:
- Site: Visibility, Privacy, Bot & Spam, Reports, Integrations
- Workspace: Members, Notifications, Audit Log
- Account: Security, Devices

Old settings pages and profile modal remain functional.

components/dashboard/Sidebar.tsx

@@ -6,6 +6,7 @@ import { usePathname, useRouter } from 'next/navigation'
 import { listSites, type Site } from '@/lib/api/sites'
 import { useAuth } from '@/lib/auth/context'
 import { useSettingsModal } from '@/lib/settings-modal-context'
+import { useUnifiedSettings } from '@/lib/unified-settings-context'
 import { getUserOrganizations, switchContext, type OrganizationMember } from '@/lib/api/organization'
 import { setSessionAction } from '@/app/actions/auth'
 import { logger } from '@/lib/utils/logger'
@@ -443,6 +444,7 @@ export default function Sidebar({
   const pathname = usePathname()
   const router = useRouter()
   const { openSettings } = useSettingsModal()
+  const { openUnifiedSettings } = useUnifiedSettings()
   const [sites, setSites] = useState<Site[]>([])
   const [orgs, setOrgs] = useState<OrganizationMember[]>([])
   const [pendingHref, setPendingHref] = useState<string | null>(null)
@@ -478,15 +480,19 @@ export default function Sidebar({
 
   useEffect(() => {
     const handler = (e: KeyboardEvent) => {
+      const tag = (e.target as HTMLElement)?.tagName
+      if (tag === 'INPUT' || tag === 'TEXTAREA' || tag === 'SELECT') return
       if (e.key === '[' && !e.metaKey && !e.ctrlKey && !e.altKey) {
-        const tag = (e.target as HTMLElement)?.tagName
-        if (tag === 'INPUT' || tag === 'TEXTAREA' || tag === 'SELECT') return
         e.preventDefault(); toggle()
       }
+      // `,` opens unified settings (same as GitHub/Linear)
+      if (e.key === ',' && !e.metaKey && !e.ctrlKey && !e.altKey) {
+        e.preventDefault(); openUnifiedSettings()
+      }
     }
     document.addEventListener('keydown', handler)
     return () => document.removeEventListener('keydown', handler)
-  }, [collapsed])
+  }, [collapsed, openUnifiedSettings])
 
   const toggle = useCallback(() => {
     setCollapsed((prev) => { const next = !prev; localStorage.setItem(SIDEBAR_KEY, String(next)); return next })