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/templates/backend-preview.html

@@ -31,6 +31,7 @@
                             <f:case value="icon_card">✦</f:case>
                             <f:case value="feature">⭐</f:case>
                             <f:case value="compact">▫</f:case>
+                            <f:case value="flipcard">🔄</f:case>
                             <f:defaultCase>▢</f:defaultCase>
                         </f:switch>
                     </div>
@@ -65,6 +66,10 @@
             </div>
         </f:if>
 
+        <f:if condition="{data.back_headline}">
+            <div class="vitec-preview__body-text">🔄 Back: {data.back_headline}</div>
+        </f:if>
+
         <div class="vitec-preview__ctas">
             <f:if condition="{data.primary_cta_label}">
                 <span class="vitec-preview__cta-btn">{data.primary_cta_label} →</span>
@@ -90,6 +95,7 @@
                 <f:case value="icon_card">✦ Icon Card</f:case>
                 <f:case value="feature">⭐ Feature</f:case>
                 <f:case value="compact">▫ Compact</f:case>
+                <f:case value="flipcard">🔄 Flip Card</f:case>
                 <f:defaultCase>{data.layout_variant}</f:defaultCase>
             </f:switch>
         </span>