Add backend with buffered zstd-compressed report storage

Introduce the Go backend (netwatch-server) with an HTTP API that
accepts telemetry reports and persists them as zstd-compressed JSONL
files. Reports are buffered in memory and flushed to disk when the
buffer reaches 10 MiB or every 60 seconds.

backend/internal/server/routes.go

@@ -0,0 +1,31 @@
+package server
+
+import (
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+)
+
+const requestTimeout = 60 * time.Second
+
+// SetupRoutes configures the chi router with middleware and
+// all application routes.
+func (s *Server) SetupRoutes() {
+	s.router = chi.NewRouter()
+
+	s.router.Use(middleware.Recoverer)
+	s.router.Use(middleware.RequestID)
+	s.router.Use(s.mw.Logging())
+	s.router.Use(s.mw.CORS())
+	s.router.Use(middleware.Timeout(requestTimeout))
+
+	s.router.Get(
+		"/.well-known/healthcheck",
+		s.h.HandleHealthCheck(),
+	)
+
+	s.router.Route("/api/v1", func(r chi.Router) {
+		r.Post("/reports", s.h.HandleReport())
+	})
+}