Revert "feat(threads): paginate full history via summaries endpoint (#1022)" (#1037)

This reverts commit 2f47f1ced2.

backend/src/gateway/app.py

@@ -15,7 +15,6 @@ from src.gateway.routers import (
     models,
     skills,
     suggestions,
-    threads,
     uploads,
 )
 
@@ -140,10 +139,6 @@ This gateway provides custom endpoints for models, MCP configuration, skills, an
                 "name": "channels",
                 "description": "Manage IM channel integrations (Feishu, Slack, Telegram)",
             },
-            {
-                "name": "threads",
-                "description": "Thread summary and list endpoints for lightweight UI loading",
-            },
             {
                 "name": "health",
                 "description": "Health check and system status endpoints",
@@ -181,9 +176,6 @@ This gateway provides custom endpoints for models, MCP configuration, skills, an
     # Channels API is mounted at /api/channels
     app.include_router(channels.router)
 
-    # Threads API is mounted at /api/threads
-    app.include_router(threads.router)
-
     @app.get("/health", tags=["health"])
     async def health_check() -> dict:
         """Health check endpoint.