Checkpoint: headless JSON architecture documented + cleanup (Stufe 1+2)

Restore point before Stufe 3 (central resolver-service refactoring).

Includes this session's work:
- Success Story (usecase) rebuild: new fields/tabs, UsecaseSerializer,
  thin List/Show renderers, MM relations, inline content elements.
- vitec_columns content block (two-column layout with per-item content)
  incl. unified header section; special-cased JSON resolution.
- Container per-column flex (items[].config align/justify) + gap on parent.
- Unified header section across CEs/plugins/containers; header fields in JSON.
- ISO-style architecture spec: Documentation/Headless-JSON-Architecture.md.
- Cleanup: removed local scratch + verified .bak backups.
- Fixes: B-6 (undefined thumbnail variable in Downloadcardcollection image
  resolver), B-7 (unsatisfiable legacy CType OR branch in Downloadcard/Datasheets).

Rollback: git reset --hard snapshot-2026-07-09-pre-stufe3

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/vitec/Resources/Private/Language/locallang_containers.xlf

@@ -111,6 +111,73 @@
 			<trans-unit id="column.sidebar_33" resname="column.sidebar_33">
 				<source>Sidebar (33%)</source>
 			</trans-unit>
+			<trans-unit id="cards_carousel.title" resname="cards_carousel.title">
+				<source>VITEC · Cards Carousel</source>
+			</trans-unit>
+			<trans-unit id="cards_carousel.description" resname="cards_carousel.description">
+				<source>Horizontal carousel/slider. Place VITEC Card elements (or other content) inside; arrows, dots, autoplay and slides-per-view are configurable.</source>
+			</trans-unit>
+			<trans-unit id="cards_carousel.column" resname="cards_carousel.column">
+				<source>Slides</source>
+			</trans-unit>
+			<trans-unit id="cards_carousel.flexform.label" resname="cards_carousel.flexform.label">
+				<source>Carousel Settings</source>
+			</trans-unit>
+			<trans-unit id="flex.align.label" resname="flex.align.label">
+				<source>Align</source>
+			</trans-unit>
+			<trans-unit id="flex.align.flex_start" resname="flex.align.flex_start">
+				<source>flex-start</source>
+			</trans-unit>
+			<trans-unit id="flex.align.center" resname="flex.align.center">
+				<source>center</source>
+			</trans-unit>
+			<trans-unit id="flex.align.flex_end" resname="flex.align.flex_end">
+				<source>flex-end</source>
+			</trans-unit>
+			<trans-unit id="flex.align.stretch" resname="flex.align.stretch">
+				<source>stretch</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.label" resname="flex.justify.label">
+				<source>Justify</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.flex_start" resname="flex.justify.flex_start">
+				<source>flex-start</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.center" resname="flex.justify.center">
+				<source>center</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.space_between" resname="flex.justify.space_between">
+				<source>space-between</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.space_around" resname="flex.justify.space_around">
+				<source>space-around</source>
+			</trans-unit>
+			<trans-unit id="flex.justify.space_evenly" resname="flex.justify.space_evenly">
+				<source>space-evenly</source>
+			</trans-unit>
+			<trans-unit id="palette.grid" resname="palette.grid">
+				<source>Grid</source>
+			</trans-unit>
+			<trans-unit id="gap.label" resname="gap.label">
+				<source>Gap</source>
+			</trans-unit>
+			<trans-unit id="gap.option.1" resname="gap.option.1">
+				<source>1</source>
+			</trans-unit>
+			<trans-unit id="gap.option.2" resname="gap.option.2">
+				<source>2</source>
+			</trans-unit>
+			<trans-unit id="gap.option.3" resname="gap.option.3">
+				<source>3</source>
+			</trans-unit>
+			<trans-unit id="gap.option.4" resname="gap.option.4">
+				<source>4</source>
+			</trans-unit>
+			<trans-unit id="gap.option.5" resname="gap.option.5">
+				<source>5</source>
+			</trans-unit>
+
 		</body>
 	</file>
 </xliff>