feat: integrate external scheduler for prefetch task registration

Add SchedulerClient to communicate with external scheduler service for
registering volatile prefetch tasks discovered during HybridRAG searches.

- Add scheduler_client.py with full REST API for task CRUD operations
- Add scheduler_url config setting (default: http://scheduler:8090)
- Update consolidation service to use scheduler for prefetch registration
- Add scheduler health checks to startup/shutdown lifecycle

When HybridRAG classifies web content as prefetch-worthy, it now creates
scheduled tasks that periodically refresh the volatile cache via the
external scheduler service.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/core/dependencies.py

@@ -24,6 +24,7 @@ from src.clients.ollama_client import OllamaClient
 from src.clients.content_extractor import ContentExtractor
 from src.clients.paperless_client import PaperlessClient
 from src.clients.settings_client import SettingsClient
+from src.clients.scheduler_client import SchedulerClient
 from src.apis import (
     OpenMeteoProvider,
     AggregatedNewsProvider,
@@ -202,6 +203,22 @@ def get_settings_client() -> SettingsClient:
     return client
 
 
+@lru_cache
+def get_scheduler_client() -> SchedulerClient:
+    """
+    Get scheduler service client singleton.
+
+    Returns:
+        Initialized SchedulerClient for task management
+
+    Note: Used for registering prefetch tasks discovered during HybridRAG searches
+    """
+    settings = get_settings()
+    client = SchedulerClient(base_url=settings.scheduler_url)
+    logger.debug(f"Created Scheduler client: {settings.scheduler_url}")
+    return client
+
+
 # =============================================================================
 # External API Providers
 # =============================================================================
@@ -320,6 +337,7 @@ RedisDep = Annotated[aioredis.Redis, Depends(get_redis_client)]
 ContentExtractorDep = Annotated[ContentExtractor, Depends(get_content_extractor)]
 PaperlessDep = Annotated[PaperlessClient, Depends(get_paperless_client)]
 SettingsClientDep = Annotated[SettingsClient, Depends(get_settings_client)]
+SchedulerDep = Annotated[SchedulerClient, Depends(get_scheduler_client)]
 
 # External API provider dependencies
 WeatherProviderDep = Annotated[OpenMeteoProvider, Depends(get_weather_provider)]
@@ -392,6 +410,17 @@ async def startup_clients():
     else:
         logger.info("○ System settings not configured")
 
+    # Check Scheduler availability
+    try:
+        scheduler = get_scheduler_client()
+        is_healthy = await scheduler.health_check()
+        if is_healthy:
+            logger.info(f"✓ Scheduler ready: {settings.scheduler_url}")
+        else:
+            logger.warning("✗ Scheduler not responding")
+    except Exception as e:
+        logger.error(f"✗ Scheduler health check failed: {e}")
+
     # Qdrant, Wiki.js, SearXNG are lazy-initialized
     logger.info("Service clients startup complete")
 
@@ -461,6 +490,14 @@ async def shutdown_clients():
         except Exception as e:
             logger.error(f"Error closing settings client: {e}")
 
+    # Close scheduler client
+    try:
+        scheduler = get_scheduler_client()
+        await scheduler.close()
+        logger.info("✓ Scheduler client closed")
+    except Exception as e:
+        logger.error(f"Error closing scheduler client: {e}")
+
     logger.info("Service clients shutdown complete")
 
 
@@ -556,6 +593,14 @@ async def check_service_health() -> dict:
     else:
         health["system_settings"] = None  # Not configured
 
+    # Scheduler
+    try:
+        scheduler = get_scheduler_client()
+        health["scheduler"] = await scheduler.health_check()
+    except Exception as e:
+        logger.error(f"Scheduler health check failed: {e}")
+        health["scheduler"] = False
+
     return health
 
 
@@ -600,6 +645,7 @@ def get_consolidation_service() -> "ConsolidationService":
         ingestion_service=get_ingestion_service(),
         volatile_service=get_volatile_cache_service(),
         settings_client=get_settings_client(),
+        scheduler_client=get_scheduler_client(),
     )