feat: add Gin HTTP API with SSE streaming chat

internal/api/types.go

@@ -0,0 +1,19 @@
+package api
+
+type ChatRequest struct {
+	Message string `json:"message" binding:"required"`
+}
+
+type NoteRequest struct {
+	Title   string   `json:"title" binding:"required"`
+	Content string   `json:"content" binding:"required"`
+	Tags    []string `json:"tags"`
+}
+
+type NoteResponse struct {
+	ID        string   `json:"id"`
+	Title     string   `json:"title"`
+	Content   string   `json:"content"`
+	Tags      []string `json:"tags"`
+	CreatedAt string   `json:"created_at"`
+}