Implement bad connections baseline reset functionality

- Added a new field `badConnBaseline` in the `Handler` struct to store the baseline for bad connections.
- Updated the `BuildIncidents` function to utilize the effective bad connections count for incident generation.
- Introduced a new API endpoint `/api/agg/bad-connections/reset` to reset the bad connections baseline.
- Enhanced the frontend with a button to trigger the reset action, providing user feedback through toast notifications.
- Updated Svelte components to handle the reset functionality and display appropriate messages based on the operation's success or failure.

internal/aggregate/bad_baseline.go

@@ -0,0 +1,69 @@
+package aggregate
+
+import (
+	"context"
+	"net/http"
+	"time"
+)
+
+// effectiveConnectionsBad возвращает значение для порогов инцидентов: прирост от последнего сброса.
+func (h *Handler) effectiveConnectionsBad(alias string, current uint64) uint64 {
+	h.badConnBaselineMu.Lock()
+	defer h.badConnBaselineMu.Unlock()
+	b, ok := h.badConnBaseline[alias]
+	if !ok {
+		return current
+	}
+	if current < b {
+		// Счётчик на ноде уменьшился (перезапуск и т.п.) — старая отметка неприменима.
+		delete(h.badConnBaseline, alias)
+		return current
+	}
+	return current - b
+}
+
+func (h *Handler) setBadConnectionBaseline(alias string, snapshot uint64) {
+	h.badConnBaselineMu.Lock()
+	defer h.badConnBaselineMu.Unlock()
+	if h.badConnBaseline == nil {
+		h.badConnBaseline = make(map[string]uint64)
+	}
+	h.badConnBaseline[alias] = snapshot
+}
+
+// HandleResetBadConnectionsBaseline — POST /api/agg/bad-connections/reset
+// Сохраняет текущий connections_bad_total по каждой выбранной ноде как нулевую отметку для алертов.
+func (h *Handler) HandleResetBadConnectionsBaseline(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		w.Header().Set("Allow", http.MethodPost)
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	aliases, err := h.resolveAliases(r)
+	if err != nil {
+		writeBadRequest(w, err)
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 60*time.Second)
+	defer cancel()
+
+	type row struct {
+		Alias    string `json:"alias"`
+		OK       bool   `json:"ok"`
+		Baseline uint64 `json:"baseline,omitempty"`
+		Error    string `json:"error,omitempty"`
+	}
+	rows := make([]row, 0, len(aliases))
+	partial := false
+	for _, alias := range aliases {
+		data, meta := FetchTelemtGET[statsSummaryLite](ctx, h.Client, h.Parsed, alias, "stats/summary")
+		if !meta.OK {
+			partial = true
+			rows = append(rows, row{Alias: alias, OK: false, Error: meta.Error})
+			continue
+		}
+		h.setBadConnectionBaseline(alias, data.ConnectionsBadTotal)
+		rows = append(rows, row{Alias: alias, OK: true, Baseline: data.ConnectionsBadTotal})
+	}
+	writeAggOK(w, partial, map[string]any{"servers": rows})
+}