Route the delivery tests' gorm.Open through gormlog (closes #462)

Six test-only gorm.Open calls in internal/delivery passed a bare gorm.Config, leaving the unfiltered idiom in the tree to be copied into production code, where every gorm.Open goes through gormlog.New. They now pass gormlog.New over a logger that discards, so no gorm.Open in the tree uses a bare gorm.Config. The stale sentence saying the tree has one test-only (*gorm.DB).Scan caller is corrected in the README and in the ParamsFilter comment: only tests call Scan, and what a test binds is fixture data. Test and documentation change only.

Model: opus-5-5

internal/gormlog/gormlog.go

@@ -111,9 +111,9 @@ func (l *Logger) LogMode(gormlogger.LogLevel) gormlogger.Interface {
 //
 // One GORM path does not consult this: (*gorm.DB).Scan records the
 // statement through gorm's own traceRecorder, which does not implement
-// this interface. No production code path calls it; its one caller is
-// internal/database/database_test.go:91, whose SELECT 1 binds nothing.
-// scan_guard_test.go fails if a non-test file calls it.
+// this interface. No production code path calls it; only tests do, and
+// what a test binds is fixture data. scan_guard_test.go fails if a
+// non-test file calls it.
 // (*gorm.DB).Pluck, Row and Raw all run through the normal callback
 // processor and are filtered.
 func (l *Logger) ParamsFilter(