feat: scaffold traefik-llmgateway plugin skeleton with manifest

errors.go

@@ -0,0 +1,26 @@
+package traefikllmgateway
+
+import (
+	"encoding/json"
+	"net/http"
+	"runtime/debug"
+)
+
+// writeOAIError writes an OpenAI-compatible error envelope:
+// {"error":{"message":...,"type":...,"code":...}}.
+func writeOAIError(w http.ResponseWriter, status int, errType, msg string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(map[string]any{
+		"error": map[string]any{"message": msg, "type": errType, "code": status},
+	})
+}
+
+// recoverPanic recovers a panic from a handler, logs it, and writes a 500
+// error envelope instead of letting the panic escape ServeHTTP.
+func recoverPanic(w http.ResponseWriter, g *Gateway) {
+	if rec := recover(); rec != nil {
+		g.errorf("panic recovered: %v\n%s", rec, debug.Stack())
+		writeOAIError(w, http.StatusInternalServerError, "server_error", "internal error")
+	}
+}