Fix 500 error on knowledge base Process Documents

knowledge_base_service and analysis_service were local variables inside
the lifespan() function — not module-level exports. Importing them via
'from app.main import ...' always failed with ImportError → 500.

Use request.app.state (same pattern as analysis_routes.py) instead.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/knowledge_base_routes.py

@@ -2,7 +2,7 @@
 import difflib
 import uuid
 
-from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, UploadFile, File
+from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, Request, UploadFile, File
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.knowledge_base_schemas import (
@@ -220,12 +220,13 @@ async def delete_source_document(
 @kb_router.post("/{kb_id}/process", response_model=ProcessingJobResponse, status_code=201)
 async def trigger_processing(
     kb_id: uuid.UUID,
+    request: Request,
     background_tasks: BackgroundTasks,
     db: AsyncSession = Depends(get_db),
     user: dict = Depends(get_current_user),
 ):
     """Trigger the document processing pipeline for a knowledge base."""
-    from app.main import knowledge_base_service as kb_service
+    kb_service = getattr(request.app.state, "knowledge_base_service", None)
 
     if kb_service is None:
         raise HTTPException(
@@ -448,6 +449,7 @@ async def get_spec_diff(
 async def activate_spec_version(
     kb_id: uuid.UUID,
     version_id: uuid.UUID,
+    request: Request,
     db: AsyncSession = Depends(get_db),
     user: dict = Depends(get_current_user),
 ):
@@ -460,7 +462,7 @@ async def activate_spec_version(
     # Invalidate reference docs cache
     kb = await repo.get_knowledge_base(kb_id)
     if kb:
-        from app.main import analysis_service
+        analysis_service = getattr(request.app.state, "analysis_service", None)
         if analysis_service:
             analysis_service.reference_docs.invalidate_cache(kb.agent_key)