Add custom types, version command, and restore --verify flag

- Add internal/types package with type-safe wrappers for IDs, hashes,
  paths, and credentials (FileID, BlobID, ChunkHash, etc.)
- Implement driver.Valuer and sql.Scanner for UUID-based types
- Add `vaultik version` command showing version, commit, go version
- Add `--verify` flag to restore command that checksums all restored
  files against expected chunk hashes with progress bar
- Remove fetch.go (dead code, functionality in restore)
- Clean up TODO.md, remove completed items
- Update all database and snapshot code to use new custom types

internal/snapshot/backup_test.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"git.eeqj.de/sneak/vaultik/internal/database"
+	"git.eeqj.de/sneak/vaultik/internal/types"
 )
 
 // MockS3Client is a mock implementation of S3 operations for testing
@@ -138,13 +139,13 @@ func TestBackupWithInMemoryFS(t *testing.T) {
 	}
 
 	for _, file := range files {
-		if !expectedFiles[file.Path] {
+		if !expectedFiles[file.Path.String()] {
 			t.Errorf("Unexpected file in database: %s", file.Path)
 		}
-		delete(expectedFiles, file.Path)
+		delete(expectedFiles, file.Path.String())
 
 		// Verify file metadata
-		fsFile := testFS[file.Path]
+		fsFile := testFS[file.Path.String()]
 		if fsFile == nil {
 			t.Errorf("File %s not found in test filesystem", file.Path)
 			continue
@@ -294,8 +295,8 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 	hostname, _ := os.Hostname()
 	snapshotID := time.Now().Format(time.RFC3339)
 	snapshot := &database.Snapshot{
-		ID:             snapshotID,
-		Hostname:       hostname,
+		ID:             types.SnapshotID(snapshotID),
+		Hostname:       types.Hostname(hostname),
 		VaultikVersion: "test",
 		StartedAt:      time.Now(),
 		CompletedAt:    nil,
@@ -340,7 +341,7 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 
 		// Create file record in a short transaction
 		file := &database.File{
-			Path:  path,
+			Path:  types.FilePath(path),
 			Size:  info.Size(),
 			Mode:  uint32(info.Mode()),
 			MTime: info.ModTime(),
@@ -392,7 +393,7 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 				// Create new chunk in a short transaction
 				err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
 					chunk := &database.Chunk{
-						ChunkHash: chunkHash,
+						ChunkHash: types.ChunkHash(chunkHash),
 						Size:      int64(n),
 					}
 					return b.repos.Chunks.Create(ctx, tx, chunk)
@@ -408,7 +409,7 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 				fileChunk := &database.FileChunk{
 					FileID:    file.ID,
 					Idx:       chunkIndex,
-					ChunkHash: chunkHash,
+					ChunkHash: types.ChunkHash(chunkHash),
 				}
 				return b.repos.FileChunks.Create(ctx, tx, fileChunk)
 			})
@@ -419,7 +420,7 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 			// Create chunk-file mapping in a short transaction
 			err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
 				chunkFile := &database.ChunkFile{
-					ChunkHash:  chunkHash,
+					ChunkHash:  types.ChunkHash(chunkHash),
 					FileID:     file.ID,
 					FileOffset: int64(chunkIndex * defaultChunkSize),
 					Length:     int64(n),
@@ -463,10 +464,11 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 		}
 
 		// Create blob entry in a short transaction
+		blobID := types.NewBlobID()
 		err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
 			blob := &database.Blob{
-				ID:        "test-blob-" + blobHash[:8],
-				Hash:      blobHash,
+				ID:        blobID,
+				Hash:      types.BlobHash(blobHash),
 				CreatedTS: time.Now(),
 			}
 			return b.repos.Blobs.Create(ctx, tx, blob)
@@ -481,8 +483,8 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 		// Create blob-chunk mapping in a short transaction
 		err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
 			blobChunk := &database.BlobChunk{
-				BlobID:    "test-blob-" + blobHash[:8],
-				ChunkHash: chunkHash,
+				BlobID:    blobID,
+				ChunkHash: types.ChunkHash(chunkHash),
 				Offset:    0,
 				Length:    chunk.Size,
 			}
@@ -494,7 +496,7 @@ func (b *BackupEngine) Backup(ctx context.Context, fsys fs.FS, root string) (str
 
 		// Add blob to snapshot in a short transaction
 		err = b.repos.WithTx(ctx, func(ctx context.Context, tx *sql.Tx) error {
-			return b.repos.Snapshots.AddBlob(ctx, tx, snapshotID, "test-blob-"+blobHash[:8], blobHash)
+			return b.repos.Snapshots.AddBlob(ctx, tx, snapshotID, blobID, types.BlobHash(blobHash))
 		})
 		if err != nil {
 			return "", err