feat: H1 conversion on the API, markdown and import paths

- the /_journal/api/v1 post writes convert default and translated content
  in the write transaction and answer an additive notices key
- journal:import-posts converts and prints the converted count
  (ImportFromDirConfig, ImportStats.H1Converted)
- a category's pillar text saved in the admin answers
  editor.h1_converted_category
- every GET /categories row reports content_h1_to_h2 (additive key)

classes/blog_editor.go

@@ -13,6 +13,7 @@ import (
 	"unicode"
 	"unicode/utf8"
 
+	"git.golem15.com/golem15/sm-journal-plugin/models"
 	"git.golem15.com/golem15/summercms/modules/backpack"
 	"git.golem15.com/golem15/summercms/modules/compass"
 	"git.golem15.com/golem15/summercms/modules/pact"
@@ -35,6 +36,9 @@ const (
 	// EditorH1Converted is the notice of a save that turned H1 headings
 	// into H2 (Count is the number of headings).
 	EditorH1Converted = "golem15.journal::lang.editor.h1_converted"
+	// EditorH1ConvertedCategory is EditorH1Converted for a category's
+	// pillar text, which names the category name instead of the post title.
+	EditorH1ConvertedCategory = "golem15.journal::lang.editor.h1_converted_category"
 )
 
 // blogListValueRunes is how many runes of text a list column shows.
@@ -153,8 +157,9 @@ func checkUploadFolder(folder string) error {
 
 // decodeBlogHTMLFor is the Blog Editor types' Decode: decodeBlogHTML, then,
 // while the H1 setting is on (EffectiveH1ToH2 on the save transaction and
-// the booted application's config), ConvertH1 on the stored HTML with the
-// EditorH1Converted notice counting the converted headings. app may be nil
+// the booted application's config), ConvertH1 on the stored HTML with a
+// notice counting the converted headings: EditorH1ConvertedCategory on a
+// category's pillar text, EditorH1Converted otherwise. app may be nil
 // or answer nil; the setting is then read from the database alone.
 func decodeBlogHTMLFor(app func() *backpack.App) func(context.Context, pact.FormFieldValue) (pact.FormFieldDecoded, error) {
 	return func(ctx context.Context, in pact.FormFieldValue) (pact.FormFieldDecoded, error) {
@@ -174,11 +179,21 @@ func decodeBlogHTMLFor(app func() *backpack.App) func(context.Context, pact.Form
 			return out, nil
 		}
 		out.Value = converted
-		out.Notices = append(out.Notices, pact.FormFieldNotice{Message: EditorH1Converted, Count: n})
+		out.Notices = append(out.Notices, pact.FormFieldNotice{Message: h1ConvertedNotice(in.Record), Count: n})
 		return out, nil
 	}
 }
 
+// h1ConvertedNotice is the conversion notice for the saved record: the
+// category phrase for a category, the post phrase otherwise.
+func h1ConvertedNotice(record any) string {
+	switch record.(type) {
+	case *models.Category, models.Category:
+		return EditorH1ConvertedCategory
+	}
+	return EditorH1Converted
+}
+
 // appConfig is the config of the application app answers, nil when there
 // is none.
 func appConfig(app func() *backpack.App) *compass.Config {