Finish the lint remediation: script/cibuild exits 0 (closes #61)

Clears the final 80 golangci-lint findings under the canonical
.golangci.yml (sha256 021cc83f4e6fc7c31b95b34b846723dfcf20b66b7baeea1dc40406e643346bcb),
taking the repo from red to green: script/cibuild exits 0.

- wsl_v5 (60): blank line above defer/go statements sharing no variable
  with the line above; blank-line-only diff.
- sqlclosecheck (10): the package-local CloseRows helper hid the close
  from the analyzer. Helper removed; all 18 call sites now defer an
  inline rows.Close(), preserving the fatal-on-close-error path. No
  resource leak existed - the rows were always being closed.
- prealloc (3): append targets given a starting capacity.
- revive (3): package-name findings suppressed with per-site directives
  pending the naming decision tracked in #76.

No gosec suppressions are needed under the pinned linter. .golangci.yml,
Dockerfile, Makefile, .gitea/ and script/ are byte-identical to main.

Verified with script/cibuild (digest-pinned golangci-lint v2.12.2), not
make check - the latter resolves the linter from PATH and is not a
trustworthy gate here; see #78.

Closes #59.

internal/snapshot/snapshot.go

@@ -259,6 +259,7 @@ func (sm *SnapshotManager) ExportSnapshotMetadata(
 	}
 
 	log.Debug("Created temporary directory", "path", tempDir)
+
 	defer func() {
 		log.Debug("Cleaning up temporary directory", "path", tempDir)
 
@@ -555,6 +556,7 @@ func (sm *SnapshotManager) cleanSnapshotDB(
 	if err != nil {
 		return nil, fmt.Errorf("opening temp database: %w", err)
 	}
+
 	defer func() {
 		err := db.Close()
 		if err != nil {
@@ -567,6 +569,7 @@ func (sm *SnapshotManager) cleanSnapshotDB(
 	if err != nil {
 		return nil, fmt.Errorf("beginning transaction: %w", err)
 	}
+
 	defer func() {
 		rbErr := tx.Rollback()
 		if rbErr != nil && !errors.Is(rbErr, sql.ErrTxDone) {
@@ -685,6 +688,7 @@ func (sm *SnapshotManager) compressFile(inputPath, outputPath string) error {
 	if err != nil {
 		return fmt.Errorf("opening input file: %w", err)
 	}
+
 	defer func() {
 		err := input.Close()
 		if err != nil {
@@ -696,6 +700,7 @@ func (sm *SnapshotManager) compressFile(inputPath, outputPath string) error {
 	if err != nil {
 		return fmt.Errorf("creating output file: %w", err)
 	}
+
 	defer func() {
 		err := output.Close()
 		if err != nil {
@@ -714,6 +719,7 @@ func (sm *SnapshotManager) compressFile(inputPath, outputPath string) error {
 
 	// Track if writer has been closed to avoid double-close
 	writerClosed := false
+
 	defer func() {
 		if !writerClosed {
 			err := writer.Close()
@@ -749,6 +755,7 @@ func (sm *SnapshotManager) copyFile(src, dst string) error {
 	if err != nil {
 		return err
 	}
+
 	defer func() {
 		log.Debug("Closing source file", "path", src)
 
@@ -764,6 +771,7 @@ func (sm *SnapshotManager) copyFile(src, dst string) error {
 	if err != nil {
 		return err
 	}
+
 	defer func() {
 		log.Debug("Closing destination file", "path", dst)
 
@@ -794,6 +802,7 @@ func (sm *SnapshotManager) generateBlobManifest(
 	if err != nil {
 		return nil, fmt.Errorf("opening database: %w", err)
 	}
+
 	defer func() { _ = db.Close() }()
 
 	// Create repositories to access the data