feat: implement RAG-based chatbot service with daily usage rate limiting and background index worker

internal/models/rag.go

@@ -15,3 +15,25 @@ type RagChunk struct {
 	CreatedAt  time.Time `json:"created_at"`
 	UpdatedAt  time.Time `json:"updated_at"`
 }
+
+type RagIndexTask struct {
+	ProjectID       string           `json:"project_id"`
+	DeleteWikiIDs   []string         `json:"delete_wiki_ids"`
+	DeleteEntityIDs []string         `json:"delete_entity_ids"`
+	Wikis           []*RagWikiItem   `json:"wikis"`
+	Entities        []*RagEntityItem `json:"entities"`
+}
+
+type RagWikiItem struct {
+	ID     string `json:"id"`
+	Title  string `json:"title"`
+	Doc    string `json:"doc"`
+	Source string `json:"source"`
+}
+
+type RagEntityItem struct {
+	ID          string `json:"id"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	Source      string `json:"source"`
+}