Add reliability improvements and config persistence feature

- Implement context cleanup with sync.Once and io.Closer interface
- Add regex-based error classification for robust error handling
- Create ProcessManager with thread-safe process tracking
- Add disk space caching with 30s TTL for performance
- Implement metrics collection with structured logging
- Add config persistence (.dbbackup.conf) for directory-local settings
- Auto-save/auto-load configuration with --no-config and --no-save-config flags
- Successfully tested with 42GB d7030 database (35K large objects, 36min backup)
- All cross-platform builds working (9/10 platforms)

internal/tui/menu.go

@@ -3,7 +3,9 @@ package tui
 import (
 	"context"
 	"fmt"
+	"io"
 	"strings"
+	"sync"
 
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
@@ -61,8 +63,9 @@ type MenuModel struct {
 	dbTypeCursor    int
 
 	// Background operations
-	ctx    context.Context
-	cancel context.CancelFunc
+	ctx       context.Context
+	cancel    context.CancelFunc
+	closeOnce sync.Once
 }
 
 func NewMenuModel(cfg *config.Config, log logger.Logger) MenuModel {
@@ -109,6 +112,19 @@ func NewMenuModel(cfg *config.Config, log logger.Logger) MenuModel {
 	return model
 }
 
+// Close implements io.Closer for safe cleanup
+func (m *MenuModel) Close() error {
+	m.closeOnce.Do(func() {
+		if m.cancel != nil {
+			m.cancel()
+		}
+	})
+	return nil
+}
+
+// Ensure MenuModel implements io.Closer
+var _ io.Closer = (*MenuModel)(nil)
+
 // Init initializes the model
 func (m MenuModel) Init() tea.Cmd {
 	return nil

internal/tui/progress.go

@@ -252,6 +252,12 @@ func (s *SilentLogger) Time(msg string, args ...any)  {}
 func (s *SilentLogger) StartOperation(name string) logger.OperationLogger {
 	return &SilentOperation{}
 }
+func (s *SilentLogger) WithFields(fields map[string]interface{}) logger.Logger {
+	return s
+}
+func (s *SilentLogger) WithField(key string, value interface{}) logger.Logger {
+	return s
+}
 
 // SilentOperation implements logger.OperationLogger but doesn't output anything
 type SilentOperation struct{}