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/storage/attach_linux.go

@@ -182,8 +182,14 @@ func FinalizeAttach(req AttachRequest, progress chan<- FormatProgress) (string,
 		progress <- FormatProgress{Step: "error", Message: msg, Error: errStr, Percent: 0}
 		return fmt.Errorf("%s: %w", msg, err)
 	}
+	dbg := func(format string, args ...interface{}) {
+		if req.Logger != nil && req.Debug {
+			req.Logger.Printf("[DEBUG] FinalizeAttach: "+format, args...)
+		}
+	}
 
 	mountPath := "/mnt/" + req.MountName
+	dbg("starting: device=%s mountName=%s subPath=%s", req.DevicePath, req.MountName, req.SubPath)
 
 	// --- Step 1: Validate ---
 	send("validating", "Paraméterek ellenőrzése...", 5)
@@ -244,6 +250,7 @@ func FinalizeAttach(req AttachRequest, progress chan<- FormatProgress) (string,
 	subRel := strings.TrimPrefix(cleanSub, rawMountPath)
 	subRel = strings.TrimPrefix(subRel, "/")
 
+	dbg("raw mount path: %s, sub relative: %q", rawMountPath, subRel)
 	send("mounting", "fstab bejegyzések hozzáadása...", 35)
 
 	// Backup fstab (non-fatal)
@@ -251,13 +258,17 @@ func FinalizeAttach(req AttachRequest, progress chan<- FormatProgress) (string,
 
 	// Fstab entry 1: raw partition mount
 	// Use nofail so a missing disk doesn't block boot
+	dbg("fstab entry 1: UUID=%s → %s (fstype=%s)", uuid, rawMountPath, fsType)
 	if err := AppendFstabEntry(FstabPath, uuid, rawMountPath, fsType, "defaults,nofail,noatime"); err != nil {
+		dbg("fstab raw mount entry failed: %v", err)
 		return "", fail("mounting", "fstab bejegyzés hozzáadása sikertelen (raw mount)", err)
 	}
 
 	// Fstab entry 2: bind mount from subfolder to final path
 	bindSource := cleanSub
+	dbg("fstab entry 2: bind %s → %s", bindSource, mountPath)
 	if err := appendBindFstabEntry(FstabPath, bindSource, mountPath); err != nil {
+		dbg("fstab bind entry failed: %v", err)
 		// Roll back the raw mount fstab entry
 		_ = RemoveFstabEntry(FstabPath, uuid)
 		return "", fail("mounting", "fstab bejegyzés hozzáadása sikertelen (bind mount)", err)
@@ -272,20 +283,25 @@ func FinalizeAttach(req AttachRequest, progress chan<- FormatProgress) (string,
 		return "", fail("mounting", "Csatlakoztatási mappa nem hozható létre: "+mountPath, err)
 	}
 
+	dbg("bind mount: mount --bind %s %s", cleanSub, mountPath)
 	if out, err := exec.Command("mount", "--bind", cleanSub, mountPath).CombinedOutput(); err != nil {
+		dbg("bind mount failed: %s", string(out))
 		_ = RemoveFstabEntry(FstabPath, uuid)
 		_ = removeBindFstabEntry(FstabPath, mountPath)
 		return "", fail("mounting", "Bind mount sikertelen: "+string(out), err)
 	}
 
 	// Verify bind mount
+	dbg("verifying bind mount with findmnt")
 	verifyOut, verifyErr := exec.Command("findmnt", "-n", "-o", "SOURCE", "--target", mountPath).Output()
 	if verifyErr != nil || strings.TrimSpace(string(verifyOut)) == "" {
+		dbg("bind mount verification failed: findmnt returned %q err=%v", string(verifyOut), verifyErr)
 		_ = exec.Command("umount", mountPath).Run()
 		_ = RemoveFstabEntry(FstabPath, uuid)
 		_ = removeBindFstabEntry(FstabPath, mountPath)
 		return "", fail("mounting", "A bind mount nem ellenőrizhető", fmt.Errorf("mount point %s not found after bind mount", mountPath))
 	}
+	dbg("bind mount verified: source=%q", strings.TrimSpace(string(verifyOut)))
 
 	send("mounting", "Csatlakoztatva: "+mountPath, 70)
 
@@ -301,6 +317,7 @@ func FinalizeAttach(req AttachRequest, progress chan<- FormatProgress) (string,
 		}
 	}
 
+	dbg("attach completed successfully: %s", mountPath)
 	send("done", "Meghajtó sikeresen csatolva: "+mountPath, 100)
 
 	return mountPath, nil