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/ProceduralNavigationPage.tsx

@@ -25,6 +25,7 @@ import type { CustomStepDraft } from '@/components/step-library/CustomStepModal'
 import { PostStepActionModal } from '@/components/session/PostStepActionModal'
 import { CopilotPanel } from '@/components/copilot/CopilotPanel'
 import { CopilotToggle } from '@/components/copilot/CopilotToggle'
+import { SupportingDataPanel } from '@/components/session/SupportingDataPanel'
 import { integrationsApi, sessionPsaApi } from '@/api/integrations'
 import { TicketPickerModal } from '@/components/session/TicketPickerModal'
 import { TicketLinkIndicator } from '@/components/session/TicketLinkIndicator'
@@ -792,6 +793,13 @@ export function ProceduralNavigationPage() {
               <StepFeedback stepId={currentStep.id} sessionId={session.id} />
             </div>
           )}
+
+          {/* Supporting Data */}
+          {session && (
+            <div className="mt-4">
+              <SupportingDataPanel sessionId={session.id} />
+            </div>
+          )}
         </div>
 
         {/* AI Copilot - in-flow panel */}