feat(controller): hot-reload the notification pipes

Email, ntfy and webhook kept their settings in a plain struct field copied at
construction, so editing controllerMethod in config.json wrote the file and
replaced the in-memory configuration while the running channels stayed on their
boot values.

Add Reload to the Controller interface and implement it for the three
notification pipes; Manager.ReloadAll fans an update out to every registered
controller and is wired into the reload hook from main.

Reload runs on the goroutine serving the settings update while the send methods
run on the status-change and incoming-webhook goroutines, so storing the new
settings in a plain field would be a data race. Each pipe publishes its settings
— and the HTTP client derived from them — through atomic pointers, and every
send takes one snapshot so a reload landing mid-send cannot split it across two
configurations.

Only a change to networkUseProxy rebuilds the client; everything else is read
from the settings at send time, so a reload that changes nothing relevant leaves
the client alone. Email needed one more fix: gomail exposes its dial hook as a
package-level variable with no unset, and the constructor only installed the
proxy dialer when the flag was set, so turning networkUseProxy off left SMTP
tunnelled through a proxy. applyEmailProxy now restores net.DialTimeout, which
is gomail's own default.

QQ (Napcat) and Telegram implement Reload because the interface requires it, but
neither can apply a change in place: the NapCat client is stopped through a
sync.Once and the Telegram polling context is created with the controller, so
both need to be rebuilt and swapped into the manager. Rather than no-op silently
and let an edit look applied, they log a warning while their settings diverge.
That rebuild is the next step.

internal/controller/pipes/email.go

@@ -2,6 +2,9 @@ package pipes
 
 import (
 	"fmt"
+	"net"
+	"reflect"
+	"sync/atomic"
 
 	gomail "gopkg.in/mail.v2"
 
@@ -14,20 +17,41 @@ import (
 )
 
 // EmailController handles email notifications via SMTP.
+//
+// The configuration is held behind an atomic pointer rather than in a plain
+// field: Reload replaces it on the settings-update goroutine while the send
+// methods read it on the status-change and incoming-webhook goroutines.
 type EmailController struct {
-	cfg config.EmailConfig
+	cfg atomic.Pointer[config.EmailConfig]
 }
 
 // NewEmailController creates a new Email controller.
 func NewEmailController(cfg config.EmailConfig) *EmailController {
-	if cfg.NetworkUseProxy {
-		// Route SMTP through the HTTP CONNECT proxy. NetDialTimeout is
-		// gomail's documented hook for overriding how the SMTP connection is
-		// dialed. There is a single global email channel, so overriding it
-		// unconditionally when the flag is set is safe.
+	e := &EmailController{}
+	e.cfg.Store(&cfg)
+	applyEmailProxy(cfg.NetworkUseProxy)
+	return e
+}
+
+// settings returns the configuration currently in effect. The value it points
+// at is never mutated after being stored, so a caller can hold the pointer for
+// one whole send without a concurrent Reload disturbing it.
+func (e *EmailController) settings() *config.EmailConfig {
+	return e.cfg.Load()
+}
+
+// applyEmailProxy routes SMTP through the HTTP CONNECT proxy, or restores a
+// direct dial. gomail exposes the dial path as the package-level
+// NetDialTimeout, whose own default is net.DialTimeout, so turning the proxy
+// off has to put that back rather than leave the hook in place. There is a
+// single global email channel, so setting a package-level hook here is
+// unambiguous.
+func applyEmailProxy(useProxy bool) {
+	if useProxy {
 		gomail.NetDialTimeout = netproxy.DialWithTimeout(true)
+		return
 	}
-	return &EmailController{cfg: cfg}
+	gomail.NetDialTimeout = net.DialTimeout
 }
 
 // Name returns the controller name.
@@ -37,7 +61,7 @@ func (e *EmailController) Name() string {
 
 // Start initializes the Email controller.
 func (e *EmailController) Start() error {
-	if !e.cfg.Enabled {
+	if !e.settings().Enabled {
 		postLog.Info("Email controller is disabled")
 		return nil
 	}
@@ -50,90 +74,121 @@ func (e *EmailController) Stop() {
 	postLog.Info("Email controller stopped")
 }
 
+// Reload applies the current configuration. Swapping in the new settings is
+// enough for everything read at the point of use; the proxy setting is the
+// exception, because it is baked into gomail's package-level dialer when the
+// controller is built rather than consulted per send.
+func (e *EmailController) Reload() {
+	global := config.Current()
+	if global == nil {
+		return
+	}
+
+	current := e.settings()
+	updated := global.ControllerMethod.Email
+	// EmailConfig carries a recipient slice, so it is not comparable with ==.
+	if reflect.DeepEqual(*current, updated) {
+		return
+	}
+
+	if current.NetworkUseProxy != updated.NetworkUseProxy {
+		applyEmailProxy(updated.NetworkUseProxy)
+	}
+	e.cfg.Store(&updated)
+	postLog.Debug("Email controller reloaded")
+}
+
 // IsEnabled returns whether the controller is enabled.
 func (e *EmailController) IsEnabled() bool {
-	return e.cfg.Enabled
+	return e.settings().Enabled
 }
 
 // IsMarkdown returns whether the channel renders Markdown, per its markdown
 // setting in config.json.
 func (e *EmailController) IsMarkdown() bool {
-	return e.cfg.Markdown
+	return e.settings().Markdown
 }
 
 // SendStatusChange sends a status change notification via Email.
 func (e *EmailController) SendStatusChange(change node.StatusChange) error {
-	if !e.cfg.Enabled {
+	s := e.settings()
+	if !s.Enabled {
 		return nil
 	}
-	if len(e.cfg.To) == 0 {
+	if len(s.To) == 0 {
 		postLog.Debug("Email controller has no recipients configured")
 		return nil
 	}
 
 	cfg := config.Current()
 	params := template.BuildParamsFromStatusChange(change)
-	body := template.Render(cfg.ControllerMessage.ServerStatusChanged, params, e.cfg.Markdown)
+	body := template.Render(cfg.ControllerMessage.ServerStatusChanged, params, s.Markdown)
 
 	subject := fmt.Sprintf("Server Status Change: %s - %s", change.Name, change.Event)
-	return e.sendEmail(subject, body)
+	return e.sendEmail(s, subject, body)
 }
 
 // SendServerList sends the server list via Email.
 func (e *EmailController) SendServerList(onlineServers, offlineServers string) error {
-	if !e.cfg.Enabled || len(e.cfg.To) == 0 {
+	s := e.settings()
+	if !s.Enabled || len(s.To) == 0 {
 		return nil
 	}
 
 	cfg := config.Current()
 	params := template.BuildParamsFromServerList()
-	body := template.Render(cfg.ControllerMessage.ServerList, params, e.cfg.Markdown)
+	body := template.Render(cfg.ControllerMessage.ServerList, params, s.Markdown)
 
-	return e.sendEmail("Server List", body)
+	return e.sendEmail(s, "Server List", body)
 }
 
 // SendExecuteResult sends a command execution result via Email.
 func (e *EmailController) SendExecuteResult(serverName, serverUUID, command, result string) error {
-	if !e.cfg.Enabled || len(e.cfg.To) == 0 {
+	s := e.settings()
+	if !s.Enabled || len(s.To) == 0 {
 		return nil
 	}
 
 	cfg := config.Current()
 	params := template.BuildParamsFromExecResult(serverName, serverUUID, command, result)
-	body := template.Render(cfg.ControllerMessage.ServerExecuteResult, params, e.cfg.Markdown)
+	body := template.Render(cfg.ControllerMessage.ServerExecuteResult, params, s.Markdown)
 
 	subject := fmt.Sprintf("Command Result: %s on %s", command, serverName)
-	return e.sendEmail(subject, body)
+	return e.sendEmail(s, subject, body)
 }
 
 // SendAlert sends an alert submitted through the incoming webhook API to the
 // configured recipients.
 func (e *EmailController) SendAlert(alert controller.Alert) error {
-	if !e.cfg.Enabled {
+	s := e.settings()
+	if !s.Enabled {
 		return nil
 	}
-	if len(e.cfg.To) == 0 {
+	if len(s.To) == 0 {
 		postLog.Debug("Email controller has no recipients configured")
 		return nil
 	}
 
-	return e.sendEmail(alert.Subject, alert.Render(e.cfg.Markdown))
+	return e.sendEmail(s, alert.Subject, alert.Render(s.Markdown))
 }
 
-func (e *EmailController) sendEmail(subject, body string) error {
+// sendEmail delivers one message using the settings the caller already
+// snapshotted, so the recipients the guard approved are the recipients that
+// receive it even if a reload lands mid-send.
+func (e *EmailController) sendEmail(s *config.EmailConfig, subject, body string) error {
 	m := gomail.NewMessage()
-	m.SetHeader("From", e.cfg.From)
-	m.SetHeader("To", e.cfg.To...)
+	m.SetHeader("From", s.From)
+	m.SetHeader("To", s.To...)
 	m.SetHeader("Subject", subject)
 	m.SetBody("text/plain", body)
 
-	d := gomail.NewDialer(e.cfg.SMTPHost, e.cfg.SMTPPort, e.cfg.Username, e.cfg.Password)
+	d := gomail.NewDialer(s.SMTPHost, s.SMTPPort, s.Username, s.Password)
 
 	if err := d.DialAndSend(m); err != nil {
 		postLog.Warning("Failed to send email: " + err.Error())
 		return err
 	}
 
-	postLog.Debug("Email sent successfully to " + fmt.Sprintf("%v", e.cfg.To))
+	postLog.Debug("Email sent successfully to " + fmt.Sprintf("%v", s.To))
 	return nil
 }