feat: Go backend, enhanced search, new widgets, Docker deploy

Major changes:
- Add Go backend (backend/) with microservices architecture
- Enhanced master-agents-svc: reranker, content-classifier, stealth-crawler,
  proxy-manager, media-search, fastClassifier, language detection
- New web-svc widgets: KnowledgeCard, ProductCard, ProfileCard, VideoCard,
  UnifiedCard, CardGallery, InlineImageGallery, SourcesPanel, RelatedQuestions
- Improved discover-svc with discover-db integration
- Docker deployment improvements (Caddyfile, vendor.sh, BUILD.md)
- Library-svc: project_id schema migration
- Remove deprecated finance-svc and travel-svc
- Localization improvements across services

Made-with: Cursor

backend/pkg/ndjson/writer.go

@@ -0,0 +1,113 @@
+package ndjson
+
+import (
+	"bufio"
+	"encoding/json"
+	"io"
+	"sync"
+)
+
+type Writer struct {
+	w   io.Writer
+	buf *bufio.Writer
+	mu  sync.Mutex
+}
+
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		w:   w,
+		buf: bufio.NewWriter(w),
+	}
+}
+
+func (w *Writer) Write(v interface{}) error {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	data, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+
+	if _, err := w.buf.Write(data); err != nil {
+		return err
+	}
+
+	if err := w.buf.WriteByte('\n'); err != nil {
+		return err
+	}
+
+	return w.buf.Flush()
+}
+
+func (w *Writer) WriteRaw(data []byte) error {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	if _, err := w.buf.Write(data); err != nil {
+		return err
+	}
+
+	if err := w.buf.WriteByte('\n'); err != nil {
+		return err
+	}
+
+	return w.buf.Flush()
+}
+
+func (w *Writer) Flush() error {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	return w.buf.Flush()
+}
+
+type StreamEvent struct {
+	Type    string      `json:"type"`
+	Block   interface{} `json:"block,omitempty"`
+	BlockID string      `json:"blockId,omitempty"`
+	Chunk   string      `json:"chunk,omitempty"`
+	Patch   interface{} `json:"patch,omitempty"`
+	Data    interface{} `json:"data,omitempty"`
+}
+
+func WriteBlock(w *Writer, block interface{}) error {
+	return w.Write(StreamEvent{
+		Type:  "block",
+		Block: block,
+	})
+}
+
+func WriteTextChunk(w *Writer, blockID, chunk string) error {
+	return w.Write(StreamEvent{
+		Type:    "textChunk",
+		BlockID: blockID,
+		Chunk:   chunk,
+	})
+}
+
+func WriteUpdateBlock(w *Writer, blockID string, patch interface{}) error {
+	return w.Write(StreamEvent{
+		Type:    "updateBlock",
+		BlockID: blockID,
+		Patch:   patch,
+	})
+}
+
+func WriteResearchComplete(w *Writer) error {
+	return w.Write(StreamEvent{
+		Type: "researchComplete",
+	})
+}
+
+func WriteMessageEnd(w *Writer) error {
+	return w.Write(StreamEvent{
+		Type: "messageEnd",
+	})
+}
+
+func WriteError(w *Writer, err error) error {
+	return w.Write(StreamEvent{
+		Type: "error",
+		Data: err.Error(),
+	})
+}