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/stacks/healthprobe.go

@@ -24,6 +24,8 @@ func (m *Manager) RunHealthProbes() error {
 	// Phase 1: collect targets (under lock)
 	m.mu.RLock()
 	var targets []probeTarget
+	skippedNotDue := 0
+	skippedNoContainer := 0
 	for name, stack := range m.stacks {
 		if stack.State != StateRunning && stack.State != StateUnhealthy {
 			continue
@@ -43,6 +45,12 @@ func (m *Manager) RunHealthProbes() error {
 				effectiveInterval = 10 * time.Second
 			}
 			if time.Since(stack.HealthProbe.LastCheck) < effectiveInterval {
+				skippedNotDue++
+				if m.isDebug() {
+					sinceLastCheck := time.Since(stack.HealthProbe.LastCheck).Round(time.Second)
+					m.logger.Printf("[DEBUG] [stacks] RunHealthProbes: skipping %s — last check %s ago, effective interval %s, healthy=%v",
+						name, sinceLastCheck, effectiveInterval, stack.HealthProbe.Healthy)
+				}
 				continue
 			}
 		}
@@ -50,6 +58,7 @@ func (m *Manager) RunHealthProbes() error {
 		// Find the main container to probe (matching stack name)
 		containerName := findProbeContainer(name, stack.Containers)
 		if containerName == "" {
+			skippedNoContainer++
 			continue
 		}
 
@@ -61,6 +70,11 @@ func (m *Manager) RunHealthProbes() error {
 	}
 	m.mu.RUnlock()
 
+	if m.isDebug() {
+		m.logger.Printf("[DEBUG] [stacks] RunHealthProbes: collected %d targets (%d skipped not due, %d skipped no container)",
+			len(targets), skippedNotDue, skippedNoContainer)
+	}
+
 	if len(targets) == 0 {
 		return nil
 	}