v0.24.0 — Pre-testing observability: debug logging, diagnostic dump, startup self-test

- Add [DEBUG] logging across all modules (backup, storage, sync, selfupdate,
  monitor, notify, report, assets, setup) gated behind logging.level: "debug"
- Add /api/debug/dump endpoint returning full controller state JSON (debug only)
- Add startup self-test validating 9 subsystems (Docker, dirs, storage, hub,
  restic repos, metrics DB) with pass/warn/fail summary
- New packages: internal/selftest, internal/util
- Constructor/signature changes: debug bool params, logger params on
  RunHealthCheck and BuildReport, smart watchdog probe logging

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

controller/internal/monitor/watchdog.go

@@ -58,6 +58,11 @@ type pathProbeState struct {
 	lastStatus          string // "connected", "disconnected"
 	lastProbeTime       time.Time
 	probeInterval       time.Duration
+	// Debug counters for summary logging
+	probeCount      int
+	probeOKCount    int
+	lastSummaryTime time.Time
+	totalLatency    time.Duration
 }
 
 // StorageWatchdog monitors registered storage paths and reacts to disconnection/reconnection.
@@ -95,6 +100,9 @@ func NewStorageWatchdog(
 	}
 }
 
+// isDebug returns true if the logging level is set to "debug".
+func (w *StorageWatchdog) isDebug() bool { return w.cfg.Logging.Level == "debug" }
+
 // SetAlertRefresh sets the callback to trigger alert refresh.
 func (w *StorageWatchdog) SetAlertRefresh(fn func()) {
 	w.alertRefresh = fn
@@ -164,17 +172,45 @@ func (w *StorageWatchdog) getOrCreateState(path string) *pathProbeState {
 
 // handleConnectedProbe probes a connected drive and triggers disconnect if needed.
 func (w *StorageWatchdog) handleConnectedProbe(sp settings.StoragePath, state *pathProbeState) {
+	probeStart := time.Now()
 	result := system.ProbeStoragePath(sp.Path)
+	probeLatency := time.Since(probeStart)
+
+	if w.isDebug() {
+		state.probeCount++
+		state.totalLatency += probeLatency
+	}
+
 	if result.Status == system.ProbeConnected {
 		if state.consecutiveFailures > 0 {
 			w.logger.Printf("[DEBUG] [STORAGE] Probe recovered for %s after %d failures", sp.Path, state.consecutiveFailures)
 		}
 		state.consecutiveFailures = 0
 		state.lastStatus = "connected"
+		if w.isDebug() {
+			state.probeOKCount++
+			// Every 60 probes (~5 minutes at 5s interval): emit summary
+			if state.probeCount >= 60 {
+				avgLatency := state.totalLatency / time.Duration(state.probeCount)
+				w.logger.Printf("[DEBUG] [STORAGE] Storage watchdog: %s — %d/%d probes OK (last 5m, avg %dms)",
+					sp.Path, state.probeOKCount, state.probeCount, avgLatency.Milliseconds())
+				state.probeCount = 0
+				state.probeOKCount = 0
+				state.totalLatency = 0
+				state.lastSummaryTime = time.Now()
+			}
+		}
 		return
 	}
 
 	state.consecutiveFailures++
+
+	// Debug: log immediately on unexpected failure (was connected, now failing)
+	if w.isDebug() && state.lastStatus == "connected" {
+		w.logger.Printf("[DEBUG] [STORAGE] Storage probe failed for %s (%d/%d before disconnect): %v",
+			sp.Path, state.consecutiveFailures, probeThreshold, result.Err)
+	}
+
 	w.logger.Printf("[WARN] [STORAGE] Probe failed for %s (%d/%d): %v",
 		sp.Path, state.consecutiveFailures, probeThreshold, result.Err)
 
@@ -239,6 +275,11 @@ func (w *StorageWatchdog) handleReconnectCheck(ctx context.Context, sp settings.
 		return
 	}
 
+	if w.isDebug() {
+		w.logger.Printf("[DEBUG] [STORAGE] Reconnect check for %s: UUID=%s, mountPath=%s, isAttachWizard=%v",
+			sp.Path, uuid, mountPath, isAttachWizard)
+	}
+
 	// Check if the UUID block device is present
 	uuidPath := filepath.Join(hostDevUUIDPath, uuid)
 	if _, err := os.Stat(uuidPath); err != nil {
@@ -251,6 +292,11 @@ func (w *StorageWatchdog) handleReconnectCheck(ctx context.Context, sp settings.
 	}
 	w.logger.Printf("[INFO] [STORAGE] Drive reconnected (UUID found), attempting remount: %s (%s)", sp.Path, label)
 
+	if w.isDebug() {
+		w.logger.Printf("[DEBUG] [STORAGE] UUID %s found at %s, mounting %s (raw=%s, attachWizard=%v)",
+			uuid, uuidPath, sp.Path, rawPath, isAttachWizard)
+	}
+
 	// Attempt remount
 	if err := w.remount(sp.Path, rawPath, isAttachWizard); err != nil {
 		w.logger.Printf("[ERROR] [STORAGE] Remount failed for %s: %v", sp.Path, err)
@@ -261,9 +307,17 @@ func (w *StorageWatchdog) handleReconnectCheck(ctx context.Context, sp settings.
 	verifyResult := system.ProbeStoragePath(sp.Path)
 	if verifyResult.Status != system.ProbeConnected {
 		w.logger.Printf("[ERROR] [STORAGE] Post-remount probe failed for %s: %v", sp.Path, verifyResult.Err)
+		if w.isDebug() {
+			w.logger.Printf("[DEBUG] [STORAGE] Post-mount verification failed for %s: status=%v, err=%v",
+				sp.Path, verifyResult.Status, verifyResult.Err)
+		}
 		return
 	}
 
+	if w.isDebug() {
+		w.logger.Printf("[DEBUG] [STORAGE] Post-mount verification succeeded for %s", sp.Path)
+	}
+
 	w.logger.Printf("[INFO] [STORAGE] Drive successfully remounted: %s (%s)", sp.Path, label)
 
 	// Clean stale restic locks