refactor: modularize API routes into separate files and clean up dependencies

decnet/web/router/stats/api_get_stats.py

@@ -0,0 +1,13 @@
+from typing import Any
+
+from fastapi import APIRouter, Depends
+
+from decnet.web.dependencies import get_current_user, repo
+from decnet.web.models import StatsResponse
+
+router = APIRouter()
+
+
+@router.get("/stats", response_model=StatsResponse, tags=["Observability"])
+async def get_stats(current_user: str = Depends(get_current_user)) -> dict[str, Any]:
+    return await repo.get_stats_summary()