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/health.go

@@ -0,0 +1,52 @@
+package api
+
+import (
+	"net/http"
+	"time"
+
+	"flowsight/internal/model"
+)
+
+// Health serves GET /api/health: last cycle time + credits spent today +
+// scheduler state + stale flags (docs/API.md).
+func (s *Server) Health(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Query().Get("force") == "1" {
+		_ = s.Sched.RunCycle(r.Context()) // synchronous probe cycle
+	}
+	lastCycle, schedOK := s.Sched.Status()
+	today := time.Now().Format("2006-01-02")
+	credits := s.DB.CreditsToday(today)
+	lastDate, _, _, _ := s.DB.LatestBriefing()
+	cutoff := model.StaleSession(time.Now())
+	stale := []string{}
+	if lastDate != "" {
+		if t, err := time.Parse("2006-01-02", lastDate[:10]); err == nil && t.Before(cutoff) {
+			stale = append(stale, "briefing older than one session ("+lastDate+")")
+		} else if lastDate < today {
+			stale = append(stale, "briefing older than today ("+lastDate+")")
+		}
+	}
+	if !s.Cfg.HasSectorsKey() {
+		stale = append(stale, "offline mode: SECTORS_API_KEY unset, serving seed data")
+	}
+	writeJSON(w, http.StatusOK, map[string]any{
+		"last_cycle_at": lastCycle,
+		"credits_today": credits,
+		"scheduler_ok":  schedOK,
+		"stale_flags":   stale,
+		"citations":     []model.Citation{},
+	})
+}
+
+// Accuracy serves GET /api/accuracy: per-agent {calls, resolved, hits, hit_rate}.
+func (s *Server) Accuracy(w http.ResponseWriter, r *http.Request) {
+	stats, err := s.DB.AccuracyStats()
+	if err != nil {
+		writeErr(w, http.StatusBadGateway, "db: "+err.Error())
+		return
+	}
+	if stats == nil {
+		stats = []map[string]any{}
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"agents": stats})
+}