docker (#4711)

# 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: ConnorYoh <40631091+ConnorYoh@users.noreply.github.com>

docker/unified/build.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# Build script for Stirling-PDF Unified Container
+# Usage: ./build.sh [version-tag]
+
+set -e
+
+VERSION_TAG=${1:-latest}
+IMAGE_NAME="stirlingtools/stirling-pdf:unified-${VERSION_TAG}"
+
+echo "==================================="
+echo "Building Stirling-PDF Unified Container"
+echo "Version: $VERSION_TAG"
+echo "Image: $IMAGE_NAME"
+echo "==================================="
+
+# Navigate to repository root (assuming script is in docker/unified/)
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+REPO_ROOT="$SCRIPT_DIR/../.."
+
+cd "$REPO_ROOT"
+
+# Build the image
+docker build \
+  --build-arg VERSION_TAG="$VERSION_TAG" \
+  -t "$IMAGE_NAME" \
+  -f docker/Dockerfile.unified \
+  .
+
+echo "==================================="
+echo "✓ Build complete!"
+echo "Image: $IMAGE_NAME"
+echo ""
+echo "Test the image:"
+echo "  MODE=BOTH:     docker run -p 8080:8080 -e MODE=BOTH $IMAGE_NAME"
+echo "  MODE=FRONTEND: docker run -p 8080:8080 -e MODE=FRONTEND $IMAGE_NAME"
+echo "  MODE=BACKEND:  docker run -p 8080:8080 -e MODE=BACKEND $IMAGE_NAME"
+echo "==================================="