feat: add webhook support for /llm/job endpoint

Add comprehensive webhook notification support for the /llm/job endpoint,
following the same pattern as the existing /crawl/job implementation.

Changes:
- Add webhook_config field to LlmJobPayload model (job.py)
- Implement webhook notifications in process_llm_extraction() with 4
  notification points: success, provider validation failure, extraction
  failure, and general exceptions (api.py)
- Store webhook_config in Redis task data for job tracking
- Initialize WebhookDeliveryService with exponential backoff retry logic
Documentation:
- Add Example 6 to WEBHOOK_EXAMPLES.md showing LLM extraction with webhooks
- Update Flask webhook handler to support both crawl and llm_extraction tasks
- Add TypeScript client examples for LLM jobs
- Add comprehensive examples to docker_webhook_example.py with schema support
- Clarify data structure differences between webhook and API responses

Testing:
- Add test_llm_webhook_feature.py with 7 validation tests (all passing)
- Verify pattern consistency with /crawl/job implementation
- Add implementation guide (WEBHOOK_LLM_JOB_IMPLEMENTATION.md)

test_webhook_implementation.py

@@ -14,7 +14,8 @@ import json
 from datetime import datetime, timezone
 
 # Add deploy/docker to path to import modules
-sys.path.insert(0, '/home/user/crawl4ai/deploy/docker')
+# sys.path.insert(0, '/home/user/crawl4ai/deploy/docker')
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'deploy', 'docker'))
 
 def test_imports():
     """Test that all webhook-related modules can be imported"""
@@ -237,7 +238,8 @@ def test_api_integration():
 
     try:
         # Check if api.py can import webhook module
-        with open('/home/user/crawl4ai/deploy/docker/api.py', 'r') as f:
+        api_path = os.path.join(os.path.dirname(__file__), 'deploy', 'docker', 'api.py')
+        with open(api_path, 'r') as f:
             api_content = f.read()
 
         if 'from webhook import WebhookDeliveryService' in api_content: