feat(webui): server-side SVG charts + reanimator-chart viewer

Metrics:
- Replace canvas JS charts with server-side SVG via go-analyze/charts
- Add ring buffers (120 samples) for CPU temp and power
- /api/metrics/chart/{name}.svg endpoint serves live SVG, polled every 2s

Dashboard:
- Replace custom renderViewerPage with viewer.RenderHTML() from reanimator/chart submodule
- Mount chart static assets at /chart/static/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/server.go

@@ -8,9 +8,14 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
+	"time"
 
 	"bee/audit/internal/app"
 	"bee/audit/internal/runtimeenv"
+	gocharts "github.com/go-analyze/charts"
+	"reanimator/chart/viewer"
+	"reanimator/chart/web"
 )
 
 const defaultTitle = "Bee Hardware Audit"
@@ -24,10 +29,49 @@ type HandlerOptions struct {
 	RuntimeMode runtimeenv.Mode
 }
 
+// metricsRing holds a rolling window of live metric samples.
+type metricsRing struct {
+	mu     sync.Mutex
+	vals   []float64
+	labels []string
+	size   int
+}
+
+func newMetricsRing(size int) *metricsRing {
+	return &metricsRing{size: size, vals: make([]float64, 0, size), labels: make([]string, 0, size)}
+}
+
+func (r *metricsRing) push(v float64) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if len(r.vals) >= r.size {
+		r.vals = r.vals[1:]
+		r.labels = r.labels[1:]
+	}
+	r.vals = append(r.vals, v)
+	r.labels = append(r.labels, time.Now().Format("15:04"))
+}
+
+func (r *metricsRing) snapshot() ([]float64, []string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	v := make([]float64, len(r.vals))
+	l := make([]string, len(r.labels))
+	copy(v, r.vals)
+	copy(l, r.labels)
+	return v, l
+}
+
 // handler is the HTTP handler for the web UI.
 type handler struct {
-	opts HandlerOptions
-	mux  *http.ServeMux
+	opts       HandlerOptions
+	mux        *http.ServeMux
+	ringCPUTemp *metricsRing
+	ringPower   *metricsRing
+	ringFans    []*metricsRing
+	ringGPUTemp []*metricsRing
+	ringGPUUtil []*metricsRing
+	ringsMu     sync.Mutex
 }
 
 // NewHandler creates the HTTP mux with all routes.
@@ -42,7 +86,11 @@ func NewHandler(opts HandlerOptions) http.Handler {
 		opts.RuntimeMode = runtimeenv.ModeAuto
 	}
 
-	h := &handler{opts: opts}
+	h := &handler{
+		opts:        opts,
+		ringCPUTemp: newMetricsRing(120),
+		ringPower:   newMetricsRing(120),
+	}
 	mux := http.NewServeMux()
 
 	// ── Infrastructure ──────────────────────────────────────────────────────
@@ -87,8 +135,12 @@ func NewHandler(opts HandlerOptions) http.Handler {
 	// Preflight
 	mux.HandleFunc("GET /api/preflight", h.handleAPIPreflight)
 
-	// Metrics — SSE stream of live sensor data
+	// Metrics — SSE stream of live sensor data + server-side SVG charts
 	mux.HandleFunc("GET /api/metrics/stream", h.handleAPIMetricsStream)
+	mux.HandleFunc("GET /api/metrics/chart/", h.handleMetricsChartSVG)
+
+	// Reanimator chart static assets
+	mux.Handle("GET /chart/static/", http.StripPrefix("/chart/static/", web.Static()))
 
 	// ── Pages ────────────────────────────────────────────────────────────────
 	mux.HandleFunc("GET /", h.handlePage)
@@ -181,10 +233,72 @@ func (h *handler) handleExportIndex(w http.ResponseWriter, r *http.Request) {
 
 func (h *handler) handleViewer(w http.ResponseWriter, r *http.Request) {
 	snapshot, _ := loadSnapshot(h.opts.AuditPath)
-	body := renderViewerPage(h.opts.Title, snapshot)
+	body, err := viewer.RenderHTML(snapshot, h.opts.Title)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
 	w.Header().Set("Cache-Control", "no-store")
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	_, _ = w.Write([]byte(body))
+	_, _ = w.Write(body)
+}
+
+func (h *handler) handleMetricsChartSVG(w http.ResponseWriter, r *http.Request) {
+	name := strings.TrimPrefix(r.URL.Path, "/api/metrics/chart/")
+	name = strings.TrimSuffix(name, ".svg")
+
+	var ring *metricsRing
+	var title, unit string
+	switch name {
+	case "cpu-temp":
+		ring, title, unit = h.ringCPUTemp, "CPU Temperature", "°C"
+	case "power":
+		ring, title, unit = h.ringPower, "System Power", "W"
+	default:
+		http.NotFound(w, r)
+		return
+	}
+
+	vals, labels := ring.snapshot()
+	if len(vals) == 0 {
+		vals = []float64{0}
+		labels = []string{""}
+	}
+
+	// Sparse x-axis labels
+	sparse := make([]string, len(labels))
+	step := len(labels) / 6
+	if step < 1 {
+		step = 1
+	}
+	for i := range labels {
+		if i%step == 0 {
+			sparse[i] = labels[i]
+		}
+	}
+
+	opt := gocharts.NewLineChartOptionWithData([][]float64{vals})
+	opt.Title = gocharts.TitleOption{Text: title + " (" + unit + ")"}
+	opt.XAxis.Labels = sparse
+	opt.Legend = gocharts.LegendOption{Show: gocharts.Ptr(false)}
+
+	p := gocharts.NewPainter(gocharts.PainterOptions{
+		OutputFormat: gocharts.ChartOutputSVG,
+		Width:        600,
+		Height:       180,
+	}, gocharts.PainterThemeOption(gocharts.GetTheme("grafana")))
+	if err := p.LineChart(opt); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	buf, err := p.Bytes()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	w.Header().Set("Content-Type", "image/svg+xml")
+	w.Header().Set("Cache-Control", "no-store")
+	_, _ = w.Write(buf)
 }
 
 // ── Page handler ─────────────────────────────────────────────────────────────