feat(sasch40): improve Act III, add state persistence and fix portraits

- Fix character portrait crops and version assets to portrait_v2, ensuring correct identities (resolving Nat/Verena mismatch)
- Update Schankraum scene image and configure Nginx cache-control to prevent stale asset caching
- Make secret beer tap completely invisible in tavern until clicked
- Reposition room hotspots in Act III to eliminate overlapping click targets
- Add exit button [✕] to Bavarian Gstanzl duel minigame
- Implement localStorage persistence in gameStore to maintain progress across page reloads
- Enable clean game state and storage reset when clicking "Nochmal spielen"
- Expand automated playtest script to cover Nat dialogue, duel exit, reload persistence, and game restart

projects/sasch40/frontend/nginx.conf

@@ -12,9 +12,16 @@ server {
         try_files $uri $uri/ /index.html;
     }
 
-    # Cache static assets
-    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2)$ {
-        expires 30d;
-        add_header Cache-Control "public, no-transform";
+    # Static unhashed images, audio, and media - never cache to allow instant updates
+    location ~* \.(png|jpg|jpeg|gif|ico|svg|webp|mp3|wav|ogg)$ {
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        expires -1;
+    }
+
+    # Vite bundled hashed JS/CSS assets
+    location ~* \.(js|css)$ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
     }
 }