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/supportingData.ts

@@ -0,0 +1,39 @@
+import { apiClient } from './client'
+
+export interface SupportingDataItem {
+  id: string
+  session_id: string
+  label: string
+  data_type: 'text_snippet' | 'screenshot'
+  content: string
+  content_type: string | null
+  sort_order: number
+  created_at: string
+  updated_at: string
+}
+
+export async function getSupportingData(sessionId: string): Promise<SupportingDataItem[]> {
+  const response = await apiClient.get(`/sessions/${sessionId}/supporting-data`)
+  return response.data
+}
+
+export async function createSupportingData(
+  sessionId: string,
+  data: { label: string; data_type: string; content: string; content_type?: string }
+): Promise<SupportingDataItem> {
+  const response = await apiClient.post(`/sessions/${sessionId}/supporting-data`, data)
+  return response.data
+}
+
+export async function updateSupportingData(
+  sessionId: string,
+  itemId: string,
+  data: { label?: string; content?: string }
+): Promise<SupportingDataItem> {
+  const response = await apiClient.patch(`/sessions/${sessionId}/supporting-data/${itemId}`, data)
+  return response.data
+}
+
+export async function deleteSupportingData(sessionId: string, itemId: string): Promise<void> {
+  await apiClient.delete(`/sessions/${sessionId}/supporting-data/${itemId}`)
+}