feat(tui): unified cluster backup progress display

- Add combined overall progress bar showing all phases (0-100%)
- Phase 1/3: Backing up Globals (0-15% of overall)
- Phase 2/3: Backing up Databases (15-90% of overall)
- Phase 3/3: Compressing Archive (90-100% of overall)
- Show current database name during backup
- Phase-aware progress tracking with overallPhase, phaseDesc
- Dual progress bars: overall + database count
- Consistent with cluster restore progress display

v3.42.49

main.go

@@ -16,7 +16,7 @@ import (
 
 // Build information (set by ldflags)
 var (
-	version   = "3.42.48"
+	version   = "3.42.49"
 	buildTime = "unknown"
 	gitCommit = "unknown"
 )