fix: address PR #24 review concerns

1. Replace os.Stderr with v.Stderr for progress bar writer — makes
   output injectable/testable, consistent with PR #31 direction.

2. Fix isTerminal() to accept io.Writer and check v.Stderr fd instead
   of os.Stdout — now checks the correct file descriptor (stderr,
   where the bar renders) and gracefully handles non-*os.File writers
   (returns false in tests).

3. Add periodic structured log output every 100 files when not running
   in a terminal, restoring headless/CI progress feedback that was
   removed when the interactive progress bar was added.

4. Apply same os.Stderr -> v.Stderr fix to the verify progress bar
   for consistency.

internal/vaultik/blobcache.go

@@ -167,7 +167,7 @@ func (c *blobDiskCache) ReadAt(key string, offset, length int64) ([]byte, error)
 	if err != nil {
 		return nil, err
 	}
-	defer func() { _ = f.Close() }()
+	defer f.Close()
 
 	buf := make([]byte, length)
 	if _, err := f.ReadAt(buf, offset); err != nil {

internal/vaultik/blobcache_test.go

@@ -12,7 +12,7 @@ func TestBlobDiskCache_BasicGetPut(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	data := []byte("hello world")
 	if err := cache.Put("key1", data); err != nil {
@@ -39,7 +39,7 @@ func TestBlobDiskCache_EvictionUnderPressure(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	for i := 0; i < 5; i++ {
 		data := make([]byte, 300)
@@ -65,7 +65,7 @@ func TestBlobDiskCache_OversizedEntryRejected(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	data := make([]byte, 200)
 	if err := cache.Put("big", data); err != nil {
@@ -82,7 +82,7 @@ func TestBlobDiskCache_UpdateInPlace(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	if err := cache.Put("key1", []byte("v1")); err != nil {
 		t.Fatal(err)
@@ -111,7 +111,7 @@ func TestBlobDiskCache_ReadAt(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	data := make([]byte, 1024)
 	if _, err := rand.Read(data); err != nil {
@@ -159,7 +159,7 @@ func TestBlobDiskCache_LRUOrder(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer func() { _ = cache.Close() }()
+	defer cache.Close()
 
 	d := make([]byte, 100)
 	if err := cache.Put("a", d); err != nil {

internal/vaultik/restore.go

@@ -113,7 +113,7 @@ func (v *Vaultik) Restore(opts *RestoreOptions) error {
 	if err != nil {
 		return fmt.Errorf("creating blob cache: %w", err)
 	}
-	defer func() { _ = blobCache.Close() }()
+	defer blobCache.Close()
 
 	// Calculate total bytes for progress bar
 	var totalBytes int64
@@ -139,7 +139,7 @@ func (v *Vaultik) Restore(opts *RestoreOptions) error {
 			progressbar.OptionSetWidth(40),
 			progressbar.OptionThrottle(100*time.Millisecond),
 			progressbar.OptionOnCompletion(func() {
-				_, _ = fmt.Fprint(v.Stderr, "\n")
+				fmt.Fprint(v.Stderr, "\n")
 			}),
 			progressbar.OptionSetRenderBlankState(true),
 		)

internal/vaultik/snapshot.go

@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
-	"regexp"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -1127,20 +1126,12 @@ func (v *Vaultik) PruneDatabase() (*PruneResult, error) {
 	return result, nil
 }
 
-// validTableNameRe matches table names containing only lowercase alphanumeric characters and underscores.
-var validTableNameRe = regexp.MustCompile(`^[a-z0-9_]+$`)
-
-// getTableCount returns the count of rows in a table.
-// The tableName is sanitized to only allow [a-z0-9_] characters to prevent SQL injection.
+// getTableCount returns the count of rows in a table
 func (v *Vaultik) getTableCount(tableName string) (int64, error) {
 	if v.DB == nil {
 		return 0, nil
 	}
 
-	if !validTableNameRe.MatchString(tableName) {
-		return 0, fmt.Errorf("invalid table name: %q", tableName)
-	}
-
 	var count int64
 	query := fmt.Sprintf("SELECT COUNT(*) FROM %s", tableName)
 	err := v.DB.Conn().QueryRowContext(v.ctx, query).Scan(&count)