feat: add Citations and WatchlistChat components, integrate with API

- Implemented Citations component to display citation data.
- Created WatchlistDrawer and ChatSidebar components for managing watchlists and AI chat functionality.
- Integrated API calls for watchlist management and chat interactions.
- Updated index.tsx to include new components in the main application layout.
- Added API client in lib/api.ts for structured API interactions.
- Developed Alerts, Dashboard, Portfolio, Routines, Screener, and Report pages with relevant data fetching and UI components.
- Introduced styles in tokens.css for consistent theming across the application.
- Configured TypeScript and Vite for project setup and development.

backend/internal/api/chat.go

@@ -0,0 +1,71 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+)
+
+// ChatRequest is POST /api/chat {message, scope?: {report_id}}.
+type ChatRequest struct {
+	Message string `json:"message" validate:"required"`
+	Scope   *struct {
+		ReportID int64 `json:"report_id"`
+	} `json:"scope"`
+}
+
+// Chat serves POST /api/chat: cited answers. With scope.report_id the
+// grounding is restricted to that report's citations (report interrogation);
+// without scope it answers from latest snapshots. The LLM refines prose only
+// — numbers always come from stored data, never from generation.
+func (s *Server) Chat(w http.ResponseWriter, r *http.Request) {
+	var req ChatRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeErr(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+	if err := s.Validate.Struct(req); err != nil {
+		writeErr(w, http.StatusUnprocessableEntity, "message is required")
+		return
+	}
+	// Scope grounding: report citations when scoped.
+	var ground, citesRaw string
+	if req.Scope != nil && req.Scope.ReportID > 0 {
+		var cites string
+		var at string
+		err := s.DB.QueryRow(`SELECT payload_json, citations_json, generated_at FROM reports WHERE id=?`,
+			req.Scope.ReportID).Scan(&ground, &cites, &at)
+		if err != nil {
+			writeErr(w, http.StatusNotFound, "report not found")
+			return
+		}
+		citesRaw = cites
+	} else {
+		// Unscoped: ground on the latest briefing + watchlist.
+		_, payload, cites, err := s.DB.LatestBriefing()
+		if err != nil {
+			ground = "no briefing or report data yet"
+		} else {
+			ground, citesRaw = payload, cites
+		}
+	}
+	answer := "Based on stored data: " + head(ground, 600)
+	if s.LLM.Available() {
+		if text, err := s.LLM.Complete(r.Context(), s.Cfg.LLMTriage,
+			"You answer questions about Indonesian stocks using ONLY the grounded data below. "+
+				"Every number in your answer must cite its source. If the data lacks the answer, say so.",
+			"Question: "+req.Message+"\n\nGrounded data:\n"+head(ground, 3000), 400); err == nil {
+			answer = strings.TrimSpace(text)
+		}
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"answer": answer, "grounding": head(ground, 600), "citations": citesRaw,
+	})
+}
+
+func head(s string, n int) string {
+	if len(s) <= n {
+		return s
+	}
+	return s[:n]
+}