fix🐛: Preview now sets tab.MLTBName before rendering, matching NOActionsGen

MLTBName (table_name with underscores turned to dashes, e.g. "user_profile"
-> "user-profile") is a gorm:"-" field - table.Get never fills it in, the
caller has to. NOActionsGen has done so since it existed; Preview never
did, so every template's import path that reads it
(from '@/api/{PackageName}/{MLTBName}' in vue.go.template, present in
both the pre-Vue3 template and F4's rewrite) rendered with the module
segment missing - "from '@/api/admin/'" - in the preview dialog only.
The real generated file was always correct.

Pre-existing, not introduced by this PRD, but worth fixing now: F3/F9
added two more Preview panes (the language packs) on top of an assumption
- that Preview's output stands in for what NOActionsGen actually writes -
that was never true for this field. Checked the rest of gen.go for the
same "only set on the write path" shape; MLTBName is the only one -
every other field Preview's templates read comes straight off the
sys_tables/sys_columns rows table.Get already loads.

Verified with a throwaway harness driving Gen.Preview through a real gin
Context and sqlite-backed db, parsing the JSON response and reading back
template/vue.go.template's import line. Confirmed red first (temporarily
removed the added line): "from '@/api/verify010/'". Restored it: "from
'@/api/verify010/verify-widget'".

app/other/apis/tools/gen.go

@@ -123,6 +123,14 @@ func (e Gen) Preview(c *gin.Context) {
 	}
 
 	tab, _ := table.Get(db, false)
+	// MLTBName (table_name with underscores turned to dashes) is a gorm:"-"
+	// field - table.Get never fills it in, so every template that reads it
+	// (the .vue/.ts import paths, e.g. "@/api/{PackageName}/{MLTBName}")
+	// silently rendered it empty here. NOActionsGen has set this since it
+	// existed (see below); Preview never did, which is why the two paths
+	// are not interchangeable stand-ins for each other and should not be
+	// assumed to be.
+	tab.MLTBName = strings.Replace(tab.TBName, "_", "-", -1)
 	// R2: infer a width for any column the config page left at colWidth's 0
 	// sentinel, before vue.go.template reads .ColWidth - see column_width.go.
 	applyInferredColumnWidths(tab.Columns)