fix: Handle missing package-lock.json in Docker build

Changed Dockerfile to conditionally use npm ci or npm install
depending on whether package-lock.json exists. This makes the
build more flexible while still preferring npm ci for
reproducibility when a lock file is available.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Dockerfile

@@ -9,7 +9,8 @@ WORKDIR /app
 COPY package*.json ./
 
 # Install dependencies (including devDependencies for build)
-RUN npm ci
+# Use npm ci if package-lock.json exists, otherwise use npm install
+RUN if [ -f package-lock.json ]; then npm ci; else npm install; fi
 
 # ======================
 # Stage 2: Builder