fix(security): harden TLS, timeouts, validation, logging, and token generation

- Default TLS verification on, opt-in UPKEEP_INSECURE_SKIP_VERIFY
- Alert webhooks use 10s timeout client, close response bodies
- URL input validates http/https scheme for HTTP monitors
- Stdlib logs route to stderr instead of discard
- Panic on crypto/rand failure in token generation
- Cluster startup warnings for non-HTTPS and missing secret
- Replace demo SMTP creds with obvious placeholders
- Color-coded log entries and scroll hints in logs tab

internal/cluster/cluster.go

@@ -4,35 +4,42 @@ import (
 	"fmt"
 	"go-upkeep/internal/monitor"
 	"net/http"
+	"strings"
 	"time"
 )
 
 type Config struct {
-	Mode       string // "leader" or "follower"
-	PeerURL    string // URL of the Leader (e.g., http://primary:8080)
-	SharedKey  string // Security Key
+	Mode      string // "leader" or "follower"
+	PeerURL   string // URL of the Leader (e.g., http://primary:8080)
+	SharedKey string // Security Key
 }
 
 func Start(cfg Config) {
 	if cfg.Mode == "leader" {
 		fmt.Println("Cluster: Running as LEADER (Active)")
+		if cfg.SharedKey != "" {
+			fmt.Println("WARNING: Cluster mode enabled. Ensure the HTTP server is behind a TLS-terminating proxy.")
+		}
 		monitor.SetEngineActive(true)
 		return
 	}
 
 	if cfg.Mode == "follower" {
 		fmt.Println("Cluster: Running as FOLLOWER (Passive)")
-		monitor.SetEngineActive(false) // Start passive
+		if cfg.PeerURL != "" && !strings.HasPrefix(cfg.PeerURL, "https://") {
+			fmt.Println("WARNING: Cluster peer URL is not HTTPS. Cluster secret will be sent in cleartext.")
+		}
+		monitor.SetEngineActive(false)
 		go runFollowerLoop(cfg)
 	}
 }
 
 func runFollowerLoop(cfg Config) {
 	client := http.Client{Timeout: 2 * time.Second}
-	
+
 	// Failover Configuration
 	failures := 0
-	threshold := 3 
+	threshold := 3
 
 	for {
 		time.Sleep(5 * time.Second)
@@ -44,7 +51,7 @@ func runFollowerLoop(cfg Config) {
 
 		resp, err := client.Do(req)
 		isLeaderHealthy := false
-		
+
 		if err == nil && resp.StatusCode == 200 {
 			isLeaderHealthy = true
 			resp.Body.Close()
@@ -66,4 +73,4 @@ func runFollowerLoop(cfg Config) {
 			}
 		}
 	}
-}
+}