feat: Add claim plan confirmation flow via Redis SSE

Problem:
- After wizard form submission, need to wait for claim data from n8n
- Claim data comes via Redis channel claim:plan:{session_token}
- Need to display confirmation form with claim data

Solution:
1. Backend: Added SSE endpoint /api/v1/claim-plan/{session_token}
   - Subscribes to Redis channel claim:plan:{session_token}
   - Streams claim data from n8n to frontend
   - Handles timeouts and errors gracefully

2. Frontend: Added subscription to claim:plan channel
   - StepWizardPlan: After form submission, subscribes to SSE
   - Waits for claim_plan_ready event
   - Shows loading message while waiting
   - On success: saves claimPlanData and shows confirmation step

3. New component: StepClaimConfirmation
   - Displays claim confirmation form in iframe
   - Receives claimPlanData from parent
   - Generates HTML form (placeholder - should call n8n for real HTML)
   - Handles confirmation/cancellation via postMessage

4. ClaimForm: Added conditional step for confirmation
   - Shows StepClaimConfirmation when showClaimConfirmation=true
   - Step appears after StepWizardPlan
   - Only visible when claimPlanData is available

Flow:
1. User fills wizard form → submits
2. Form data sent to n8n via /api/v1/claims/wizard
3. Frontend subscribes to SSE /api/v1/claim-plan/{session_token}
4. n8n processes data → publishes to Redis claim:plan:{session_token}
5. Backend receives → streams to frontend via SSE
6. Frontend receives → shows StepClaimConfirmation
7. User confirms → proceeds to next step

Files:
- backend/app/api/events.py: Added stream_claim_plan endpoint
- frontend/src/components/form/StepWizardPlan.tsx: Added subscribeToClaimPlan
- frontend/src/components/form/StepClaimConfirmation.tsx: New component
- frontend/src/pages/ClaimForm.tsx: Added confirmation step to steps array

SESSION_LOG_2025-11-19.md

@@ -197,3 +197,5 @@ const redisKey = `ocr_events:${sessionToken || 'temp-' + Date.now()}`;
 - `ticket_form/docs/CODE4_FIXED.js` - исправленный код узла Code4
 - `ticket_form/docs/CODE_CREATE_WEB_CONTACT_FINAL.js` - исправленный код создания контакта
 
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