vitec_card: flipcard layout + card-back fields; shared-column repair

- layout_variant gains the value "flipcard" (onChange: reload)
- "Card Back" palette in the Layout tab directly below layout_variant:
  back_headline (Text, max 100) and back_text (Textarea, richtext),
  displayCond-gated on the flipcard layout; serialised unconditionally -
  the frontend keys the back face on layout_variant, not on field
  presence (spec 7.7)
- backend preview: flipcard badge + back-headline line
- repair "[ Missing label ]" in the card selects: layout_variant /
  background_variant are columns SHARED with vitec_ctabanner, and the
  index-wise Content Blocks merge dropped four card-only values from
  the base item list. Overrides/tt_content.php now pins the base column
  to the cta-banner lists and hands vitec_card its full lists via
  columnsOverrides (respected by FormEngine and DataHandler; an items
  override can only extend, never shorten - array_replace_recursive)
- spec v1.19 incl. head-matter fix (version table was stuck at 1.17)

Server follow-up: database:updateschema "*.add,*.change" + cache:flush

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/vitec/ContentBlocks/ContentElements/card/config.yaml

@@ -99,6 +99,8 @@ fields:
     type: Select
     renderType: selectSingle
     default: vertical
+    # displayCond of the card-back fields depends on this value
+    onChange: reload
     items:
       - label: Vertical (image top, content below)
         value: vertical
@@ -116,6 +118,27 @@ fields:
         value: feature
       - label: Compact (small card, tight spacing)
         value: compact
+      - label: Flip Card (front / back)
+        value: flipcard
+
+  # Card back - only shown when layout_variant = flipcard. displayCond needs
+  # the storage column (vitec_ vendor prefix); the JSON keys stay the plain
+  # identifiers back_headline / back_text and are emitted on EVERY card
+  # (empty when unset) - the frontend keys the back face on layout_variant.
+  - identifier: card_back
+    type: Palette
+    label: Card Back
+    description: Reverse side of the card. Only used (and only shown) when the layout variant is "Flip Card".
+    fields:
+      - identifier: back_headline
+        type: Text
+        max: 100
+        displayCond: 'FIELD:vitec_layout_variant:=:flipcard'
+      - type: Linebreak
+      - identifier: back_text
+        type: Textarea
+        enableRichtext: true
+        displayCond: 'FIELD:vitec_layout_variant:=:flipcard'
 
   - identifier: background_variant
     type: Select