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/types/session.ts

@@ -103,7 +103,7 @@ export interface SessionUpdate {
 }
 
 export interface SessionExport {
-  format: 'text' | 'markdown' | 'html' | 'psa'
+  format: 'text' | 'markdown' | 'html' | 'psa' | 'pdf'
   include_timestamps?: boolean
   include_tree_info?: boolean
   include_outcome_notes?: boolean

frontend/src/types/user.ts

@@ -10,6 +10,7 @@ export interface User {
   must_change_password: boolean
   account_id: string | null
   account_role: 'owner' | 'engineer' | 'viewer' | null
+  team_id: string | null
   created_at: string
   last_login: string | null
   phone: string | null