Add conditional pnpm lockfile handling in web Dockerfile

Add fallback to install without frozen lockfile when pnpm-lock.yaml is missing, allowing builds to proceed in development environments while maintaining strict dependency locking in production when lockfile exists.

docker/web.Dockerfile

@@ -11,7 +11,12 @@ COPY packages/shared/package.json /app/packages/shared/
 COPY packages/ui/package.json /app/packages/ui/
 COPY packages/plugin-sdk/package.json /app/packages/plugin-sdk/
 
-RUN npm install -g pnpm && pnpm install --frozen-lockfile
+RUN npm install -g pnpm \
+    && if [ -f pnpm-lock.yaml ]; then \
+        pnpm install --frozen-lockfile; \
+    else \
+        pnpm install --no-frozen-lockfile; \
+    fi
 
 FROM base AS builder
 COPY --from=deps /app/node_modules /app/node_modules