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/database/repository_debug_test.go

@@ -67,7 +67,7 @@ func TestOrphanedFileCleanupDebug(t *testing.T) {
 	t.Logf("snapshot_files count before add: %d", count)
 
 	// Add file2 to snapshot
-	err = repos.Snapshots.AddFileByID(ctx, nil, snapshot.ID, file2.ID)
+	err = repos.Snapshots.AddFileByID(ctx, nil, snapshot.ID.String(), file2.ID)
 	if err != nil {
 		t.Fatalf("failed to add file to snapshot: %v", err)
 	}