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>

fix-asset-perms.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+# =============================================================================
+# VITEC — fix backend asset permissions after a deploy via the Windows sshfs mount
+# -----------------------------------------------------------------------------
+# sshfs-win (WinFsp) writes newly deployed files with mode 770 (no other-read).
+# The webserver runs as "other" (suexec) -> assets under Resources/Public and
+# public/_assets return HTTP 403 (backend icons / CSS / JS missing).
+#
+# chmod OVER the Windows mount does NOT change the real server mode, so this
+# has to run ON THE SERVER, via real SSH, as the site owner (vitecevo).
+#
+# Usage (from the live/ project root on the server):
+#     bash fix-asset-perms.sh
+# =============================================================================
+set -u
+cd "$(dirname "$0")" || exit 1
+
+echo "[perms] Project root: $(pwd)"
+echo "[perms] Setting files 644 / directories 755 under Resources/Public + _assets ..."
+find public/_assets packages/vitec/Resources/Public -type f -exec chmod 644 {} \; 2>/dev/null
+find public/_assets packages/vitec/Resources/Public -type d -exec chmod 755 {} \; 2>/dev/null
+
+echo "[perms] Flushing TYPO3 caches ..."
+if [ -x vendor/bin/typo3 ]; then
+    vendor/bin/typo3 cache:flush
+else
+    echo "[perms] (vendor/bin/typo3 not found — skip cache flush)"
+fi
+
+echo "[perms] Done."