feat: add supporting data capture, PDF export, and branding settings UI

- API clients for supporting data CRUD and team branding
- AddSupportingDataModal with text snippet and screenshot tabs (paste + upload)
- SupportingDataPanel collapsible section integrated into both session runners
- ExportPreviewModal updated with PDF format and server-side download flow
- BrandingSettings component for company name and logo management
- Expose team_id in UserResponse schema for branding endpoint access

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/AccountSettingsPage.tsx

@@ -2,6 +2,7 @@ import { useEffect, useState } from 'react'
 import { Link } from 'react-router-dom'
 import { Building2, Users, Mail, Crown, Loader2, AlertCircle, Check, X, Settings, FolderTree, Server, RefreshCw, MessageSquareText, UserCog, AlertTriangle, Clock, Plug } from 'lucide-react'
 import { PageMeta } from '@/components/common/PageMeta'
+import { BrandingSettings } from '@/components/settings/BrandingSettings'
 import { accountsApi } from '@/api/accounts'
 import type { Account, AccountMember, AccountInvite } from '@/types'
 import { TransferOwnershipModal } from '@/components/account/TransferOwnershipModal'
@@ -21,6 +22,7 @@ export function AccountSettingsPage() {
   const { isAccountOwner } = usePermissions()
   const { plan, limits, usage } = useSubscription()
   const { defaultExportFormat, setDefaultExportFormat } = useUserPreferencesStore()
+  const user = useAuthStore((s) => s.user)
   const subscription = useAuthStore((s) => s.subscription)
 
   const [account, setAccount] = useState<Account | null>(null)
@@ -587,6 +589,11 @@ export function AccountSettingsPage() {
           <span className="text-muted-foreground group-hover:text-foreground transition-colors">&rarr;</span>
         </Link>
 
+        {/* Branding Section (owners only) */}
+        {isAccountOwner && user?.team_id && (
+          <BrandingSettings teamId={user.team_id} />
+        )}
+
         {/* Preferences Section */}
         <div className="bg-card border border-border rounded-xl p-4 sm:p-6">
           <div className="flex items-center gap-2">