feat: comprehensive debug logging across all controller modules

Add detailed [DEBUG] logging to every controller module when
logging.level is set to "debug". Each module with stateful debug
uses SetDebug(bool) wired from main.go. Covers stacks, backup,
cloudflare, integrations, system, monitor, settings, scheduler,
web handlers, storage, metrics, API, selfupdate, and assets.

Also includes the app export/import (.fab bundles) feature from
v0.32.0 and its debug page integration.

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

controller/internal/monitor/pinger.go

@@ -17,6 +17,7 @@ type Pinger struct {
 	httpClient *http.Client
 	logger     *log.Logger
 	enabled    bool
+	debug      bool
 }
 
 // NewPinger creates a new Pinger from monitoring config.
@@ -31,18 +32,32 @@ func NewPinger(cfg *config.MonitoringConfig, logger *log.Logger) *Pinger {
 	}
 }
 
+// SetDebug enables or disables debug logging for the pinger.
+func (p *Pinger) SetDebug(debug bool) {
+	p.debug = debug
+}
+
 // Ping sends a success signal with optional diagnostic body.
 func (p *Pinger) Ping(uuid string, body string) error {
+	if p.debug {
+		p.logger.Printf("[DEBUG] [pinger] Ping uuid=%s body_len=%d", uuid, len(body))
+	}
 	return p.send(uuid, "", body)
 }
 
 // Fail sends a failure signal with diagnostic body.
 func (p *Pinger) Fail(uuid string, body string) error {
+	if p.debug {
+		p.logger.Printf("[DEBUG] [pinger] Fail uuid=%s body=%q", uuid, body)
+	}
 	return p.send(uuid, "/fail", body)
 }
 
 // Start sends a "job started" signal (for duration tracking).
 func (p *Pinger) Start(uuid string) error {
+	if p.debug {
+		p.logger.Printf("[DEBUG] [pinger] Start uuid=%s", uuid)
+	}
 	return p.send(uuid, "/start", "")
 }
 
@@ -56,10 +71,16 @@ func (p *Pinger) send(uuid, suffix, body string) error {
 	}
 
 	url := fmt.Sprintf("%s/ping/%s%s", p.baseURL, uuid, suffix)
+	if p.debug {
+		p.logger.Printf("[DEBUG] [pinger] send url=%s", url)
+	}
 
 	var lastErr error
 	for attempt := 0; attempt < 3; attempt++ {
 		if attempt > 0 {
+			if p.debug {
+				p.logger.Printf("[DEBUG] [pinger] retry attempt=%d uuid=%s", attempt+1, uuid)
+			}
 			time.Sleep(2 * time.Second)
 		}
 
@@ -81,7 +102,14 @@ func (p *Pinger) send(uuid, suffix, body string) error {
 		}
 		resp.Body.Close()
 
+		if p.debug {
+			p.logger.Printf("[DEBUG] [pinger] response status=%d uuid=%s", resp.StatusCode, uuid)
+		}
+
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			if p.debug {
+				p.logger.Printf("[DEBUG] [pinger] success uuid=%s", uuid)
+			}
 			return nil
 		}
 		lastErr = fmt.Errorf("HTTP %d", resp.StatusCode)