Fix: Update Dockerfile.bun paths to be relative in backend/

backend/Dockerfile.bun

@@ -2,10 +2,10 @@ FROM oven/bun:1-alpine
 
 WORKDIR /app
 
-COPY backend/package*.json ./
+COPY package*.json ./
 RUN bun install --production
 
-COPY backend/ .
+COPY . .
 
 EXPOSE 3001