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/settings/unified/tabs/AccountProfileTab.tsx

@@ -0,0 +1,17 @@
+'use client'
+
+import ProfileSettings from '@/components/settings/ProfileSettings'
+import TrustedDevicesCard from '@/components/settings/TrustedDevicesCard'
+
+export default function AccountProfileTab() {
+  return (
+    <div className="space-y-6">
+      <div>
+        <h3 className="text-base font-semibold text-white mb-1">Profile</h3>
+        <p className="text-sm text-neutral-400">Manage your personal account settings.</p>
+      </div>
+
+      <ProfileSettings activeTab="profile" borderless hideDangerZone />
+    </div>
+  )
+}