Add CACHEBUST build arg to force Docker image rebuilds

Docker's build cache was preventing Portainer from picking up
code changes. Adding a CACHEBUST ARG before COPY invalidates
all subsequent layers when the value changes.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -9,6 +9,9 @@ COPY package*.json ./
 # Install dependencies
 RUN npm ci
 
+# Cache-bust: change CACHEBUST value in docker-compose.yml to force rebuild
+ARG CACHEBUST=1
+
 # Copy source code
 COPY . .