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/api/branding.ts

@@ -0,0 +1,23 @@
+import { apiClient } from './client'
+
+export interface BrandingInfo {
+  company_display_name: string | null
+  logo_content_type: string | null
+  has_logo: boolean
+}
+
+export async function getBranding(teamId: string): Promise<BrandingInfo> {
+  const response = await apiClient.get(`/teams/${teamId}/branding`)
+  return response.data
+}
+
+export async function updateBranding(teamId: string, formData: FormData): Promise<BrandingInfo> {
+  const response = await apiClient.patch(`/teams/${teamId}/branding`, formData, {
+    headers: { 'Content-Type': 'multipart/form-data' },
+  })
+  return response.data
+}
+
+export async function deleteLogo(teamId: string): Promise<void> {
+  await apiClient.delete(`/teams/${teamId}/branding/logo`)
+}