Close sql.Rows inline so sqlclosecheck can see it (refs #61)

The ten sqlclosecheck findings were not leaks: every one of these
queries already deferred a close through the package-local CloseRows
helper. sqlclosecheck only recognises a Close call on the rows value
in the function that produced it (directly deferred, or inside a
deferred closure), so a call that hands rows to a helper reads as
unhandled.

Rather than keep a helper the linter cannot see through, drop
CloseRows and defer a closure that calls rows.Close() directly at each
of the eighteen call sites, keeping the existing fatal-on-close-error
behaviour byte for byte. The close still runs exactly once, on
function exit, after the rows have been read.

Fatalf stays; it is still used by the transaction helpers.

internal/database/errors.go

@@ -1,7 +1,6 @@
 package database
 
 import (
-	"database/sql"
 	"fmt"
 	"os"
 )
@@ -11,11 +10,3 @@ func Fatalf(format string, args ...any) {
 	fmt.Fprintf(os.Stderr, "FATAL: "+format+"\n", args...)
 	os.Exit(1)
 }
-
-// CloseRows closes rows and exits on error
-func CloseRows(rows *sql.Rows) {
-	err := rows.Close()
-	if err != nil {
-		Fatalf("failed to close rows: %v", err)
-	}
-}