npm login (#4296)

# Description of Changes

<!--
Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: a <a>

docker/frontend/Dockerfile

@@ -6,14 +6,32 @@ WORKDIR /app
 # Copy package files
 COPY frontend/package*.json ./
 
-# Install dependencies
-RUN npm ci
+# Install dependencies (uses .npmrc secret if available, otherwise anonymous)
+RUN --mount=type=secret,id=npmrc \
+    set -e && \
+    if [ -s /run/secrets/npmrc ]; then \
+      echo "Using authenticated npm registry" && \
+      echo "$(cat /run/secrets/npmrc)" > /root/.npmrc; \
+    else \
+      echo "Using anonymous npm registry (no token provided)"; \
+    fi && \
+    npm ci --loglevel=warn && \
+    rm -f /root/.npmrc
 
 # Copy source code
 COPY frontend .
 
-# Build the application
-RUN npm run build
+# Build the application (uses .npmrc secret if available, otherwise anonymous)
+RUN --mount=type=secret,id=npmrc \
+    set -e && \
+    if [ -s /run/secrets/npmrc ]; then \
+      echo "Using authenticated npm registry for build" && \
+      echo "$(cat /run/secrets/npmrc)" > /root/.npmrc; \
+    else \
+      echo "Using anonymous npm registry for build (no token provided)"; \
+    fi && \
+    npm run build && \
+    rm -f /root/.npmrc
 
 # Production stage
 FROM nginx:alpine