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/handlers.go

@@ -33,6 +33,11 @@ type Handler struct {
 
 	cacheMu sync.Mutex
 	cache   map[string]cacheEntry
+
+	// badConnBaseline хранит снимок connections_bad_total на момент сброса в UI;
+	// инциденты bad_connections_* считаются по приросту от этой отметки (в памяти процесса шлюза).
+	badConnBaselineMu sync.Mutex
+	badConnBaseline   map[string]uint64
 }
 
 // ResolveAliasesForLive resolves aliases for external endpoints (SSE/live).