feat(documents): add GET /documents endpoint and improve models

Why:
- Need to list documents to get document IDs for queries
- ProcessRequest should default to all 5 strategies
- paragraph_count should be optional (not always stored)

Changes:
- Added GET /documents endpoint with pagination
- Added DocumentListResponse model
- ProcessRequest now defaults to all 5 strategies
- DocumentResponse.paragraph_count now defaults to 0

src/documents/routes.py

@@ -14,6 +14,7 @@ from src.core.models import PaginatedResponse, StrategyName
 from src.documents.models import (
     DeleteResponse,
     DocumentResponse,
+    DocumentListResponse,
     ProcessRequest,
     ProcessResponse,
     StrategiesResponse,
@@ -24,6 +25,18 @@ from src.documents import service
 router = APIRouter()
 
 
+@router.get("/documents", response_model=DocumentListResponse)
+async def list_documents(offset: int = 0, limit: int = 50):
+    """List all uploaded documents with pagination."""
+    result = service.list_documents(offset=offset, limit=limit)
+    return DocumentListResponse(
+        items=[DocumentResponse(**doc) for doc in result["items"]],
+        total=result["total"],
+        offset=result["offset"],
+        limit=result["limit"],
+    )
+
+
 @router.post("/documents", response_model=DocumentResponse, status_code=201)
 async def upload_document(file: UploadFile = File(...)):
     """Upload a .docx file. Parses it, stores the document tree in SQLite."""