Fix Thumbnail-Generierung (magick statt convert) und DB-Migration fuer role-Spalte

- entrypoint.sh: ImageMagick 7 nutzt 'magick' statt 'convert', Auto-Detection
- database.js: Migration fuer role-Spalte bei bestehender DB (ALTER TABLE)
- main.js: Fallback auf Vollbild wenn Thumbnail fehlt (error handler)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

entrypoint.sh

@@ -3,10 +3,21 @@
 FULLS_DIR="/app/public/images/fulls"
 THUMBS_DIR="/app/public/images/thumbs"
 
+# ImageMagick 7 (Alpine) nutzt "magick" statt "convert"
+if command -v magick >/dev/null 2>&1; then
+    IM_CMD="magick"
+elif command -v convert >/dev/null 2>&1; then
+    IM_CMD="convert"
+else
+    echo "FEHLER: Weder magick noch convert gefunden! Thumbnails koennen nicht erzeugt werden."
+    IM_CMD=""
+fi
+
 # Thumbnails fuer einen Quell- und Zielordner generieren
 generate_thumbs_for_dir() {
     src_dir="$1"
     dst_dir="$2"
+    [ -z "$IM_CMD" ] && return
     mkdir -p "$dst_dir"
     for img in "$src_dir"/*; do
         [ -f "$img" ] || continue
@@ -21,7 +32,10 @@ generate_thumbs_for_dir() {
 
         if [ ! -f "$dst_dir/$filename" ] || [ "$img" -nt "$dst_dir/$filename" ]; then
             echo "Thumbnail erstellen: $dst_dir/$filename"
-            convert "$img" -resize 512x512 -quality 80 "$dst_dir/$filename" 2>/dev/null
+            $IM_CMD "$img" -resize 512x512 -quality 80 "$dst_dir/$filename"
+            if [ $? -ne 0 ]; then
+                echo "WARNUNG: Thumbnail fehlgeschlagen fuer $filename"
+            fi
         fi
     done
 }