fix: Dockerfile cache bust ARG + rm .next + correct data.instance mapping

Three fixes:
1. ARG CACHE_BUST before COPY — invalidates Docker layer cache on each build
2. rm -rf .next before npm run build — clears Turbopack cache
3. (Already committed) const instance = data?.instance — correct API response mapping

The instance detail Sheet now opens correctly, showing all sections
(Instanz, Dokploy-Resourcen, Codebase-Graph, Ereignisverlauf, Aktionen).

Dockerfile

@@ -11,6 +11,8 @@ RUN npm install --legacy-peer-deps
 # --- Stage 2: Build ---
 FROM node:24-slim AS builder
 WORKDIR /app
+# Cache bust — forces rebuild of all subsequent layers on every push
+ARG CACHE_BUST=1
 COPY --from=deps /app/node_modules ./node_modules
 COPY . .
 ENV NEXT_TELEMETRY_DISABLED=1