fix: resolve all golangci-lint errors (#699)

Fix 12 linting issues that were causing CI failures:

errcheck (8 fixes):
- cmd/bd/mol_burn.go: wrap wispStore.Close() in defer func
- cmd/bd/mol_burn.go: handle fmt.Scanln() return value
- cmd/bd/mol_squash.go: wrap wispStore.Close() in defer func (2 locations)
- cmd/bd/wisp.go: wrap wispStore.Close() in defer func (3 locations)
- internal/beads/beads.go: wrap mainStore.Close() and wispStore.Close()

gosec G104 (2 fixes):
- internal/storage/sqlite/multirepo.go: handle rows.Close() errors

misspell (1 fix):
- cmd/bd/mol_burn.go: change "Cancelled" to "Canceled"

unparam (1 fix):
- cmd/bd/mol_squash.go: use blank identifier for unused cmd parameter

All fixes follow existing patterns in the codebase:
- defer func() { _ = store.Close() }() for deferred closes
- _ = rows.Close() for explicit closes with ignored errors
- _, _ = fmt.Scanln() for ignored return values

Co-authored-by: Charles P. Cross <cpdata@users.noreply.github.com>

internal/storage/sqlite/multirepo.go

@@ -408,12 +408,12 @@ func (s *SQLiteStorage) DeleteIssuesBySourceRepo(ctx context.Context, sourceRepo
 	for rows.Next() {
 		var id string
 		if err := rows.Scan(&id); err != nil {
-			rows.Close()
+			_ = rows.Close()
 			return 0, fmt.Errorf("failed to scan issue ID: %w", err)
 		}
 		issueIDs = append(issueIDs, id)
 	}
-	rows.Close()
+	_ = rows.Close()
 	if err := rows.Err(); err != nil {
 		return 0, fmt.Errorf("failed to iterate issues: %w", err)
 	}