feat: H1 to H2 setting with the admin save conversion (tracer)

- content_h1_to_h2 and generic_anchors on the settings row (migration
  202610280001), Headings and links tab, config key
  golem15.journal.content_h1_to_h2 used when no settings row exists
- classes.ConvertH1 on the x/net/html tokenizer; the Blog Editor types
  convert while the setting is on and answer editor.h1_converted
- GET /posts/{slug} reports content_h1_to_h2 (additive key)

models/settings/fields.yaml

@@ -13,6 +13,21 @@ fields:
         type: switch
         default: false
         tab: golem15.journal::lang.journal.tab_general
+    content_h1_to_h2:
+        span: left
+        label: golem15.journal::lang.journal.h1_to_h2_label
+        comment: golem15.journal::lang.journal.h1_to_h2_comment
+        type: switch
+        default: true
+        tab: golem15.journal::lang.journal.tab_headings
+    generic_anchors:
+        span: full
+        label: golem15.journal::lang.journal.generic_anchors_label
+        comment: golem15.journal::lang.journal.generic_anchors_comment
+        type: textarea
+        size: small
+        default: "click here\nhere\nmore\nread more\nlearn more\nthis link\nlink\nkliknij tutaj\ntutaj\ntu\nwięcej\nczytaj więcej\nczytaj dalej\nten link"
+        tab: golem15.journal::lang.journal.tab_headings
     search_use_typesense:
         span: left
         label: golem15.journal::lang.journal.search_use_typesense_label