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/TreeNavigationPage.tsx

@@ -21,6 +21,7 @@ import { StepFeedback } from '@/components/session/StepFeedback'
 import { buildSessionShareUrl, getLatestActiveShareForSession } from '@/lib/sessionShare'
 import { CopilotPanel } from '@/components/copilot/CopilotPanel'
 import { CopilotToggle } from '@/components/copilot/CopilotToggle'
+import { SupportingDataPanel } from '@/components/session/SupportingDataPanel'
 import { Button } from '@/components/ui/Button'
 import { integrationsApi, sessionPsaApi } from '@/api/integrations'
 import { TicketPickerModal } from '@/components/session/TicketPickerModal'
@@ -1204,6 +1205,13 @@ export function TreeNavigationPage() {
           />
         </div>
 
+        {/* Supporting Data */}
+        {session && (
+          <div className="mt-4">
+            <SupportingDataPanel sessionId={session.id} />
+          </div>
+        )}
+
         {/* Back Button */}
         {pathTaken.length > 1 && (
           <button