Builds custom Jar (#5029)

# Description of Changes

Change jar files to contain frontend if provided with param, else
doesnt... add release artifact -server version which wont have frontend

---

## 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)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### 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.

docker/backend/Dockerfile

@@ -17,7 +17,7 @@ WORKDIR /app
 # Copy the entire project to the working directory
 COPY . .
 
-# Build the application with DISABLE_ADDITIONAL_FEATURES=false
+# Build the application (server-only JAR - no UI, includes security features controlled at runtime)
 RUN DISABLE_ADDITIONAL_FEATURES=false \
     STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -x spotlessApply -x spotlessCheck -x test -x sonarqube
@@ -44,8 +44,7 @@ LABEL org.opencontainers.image.version="${VERSION_TAG}"
 LABEL org.opencontainers.image.keywords="PDF, manipulation, backend, API, Spring Boot"
 
 # Set Environment Variables
-ENV DISABLE_ADDITIONAL_FEATURES=false \
-    VERSION_TAG=$VERSION_TAG \
+ENV VERSION_TAG=$VERSION_TAG \
     JAVA_BASE_OPTS="-XX:+UnlockExperimentalVMOptions -XX:MaxRAMPercentage=75 -XX:InitiatingHeapOccupancyPercent=20 -XX:+G1PeriodicGCInvokesConcurrent -XX:G1PeriodicGCInterval=10000 -XX:+UseStringDeduplication -XX:G1PeriodicGCSystemLoadThreshold=70" \
     JAVA_CUSTOM_OPTS="" \
     HOME=/home/stirlingpdfuser \

docker/backend/Dockerfile.fat

@@ -17,7 +17,7 @@ WORKDIR /app
 # Copy the entire project to the working directory
 COPY . .
 
-# Build the application with DISABLE_ADDITIONAL_FEATURES=false
+# Build the application (server-only JAR - no UI, includes security features controlled at runtime)
 RUN DISABLE_ADDITIONAL_FEATURES=false \
     STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -x spotlessApply -x spotlessCheck -x test -x sonarqube
@@ -35,8 +35,7 @@ COPY --from=build /app/build/libs/restart-helper.jar restart-helper.jar
 ARG VERSION_TAG
 
 # Set Environment Variables
-ENV DISABLE_ADDITIONAL_FEATURES=true \
-    VERSION_TAG=$VERSION_TAG \
+ENV VERSION_TAG=$VERSION_TAG \
     JAVA_BASE_OPTS="-XX:+UnlockExperimentalVMOptions -XX:MaxRAMPercentage=75 -XX:InitiatingHeapOccupancyPercent=20 -XX:+G1PeriodicGCInvokesConcurrent -XX:G1PeriodicGCInterval=10000 -XX:+UseStringDeduplication -XX:G1PeriodicGCSystemLoadThreshold=70" \
     JAVA_CUSTOM_OPTS="" \
     HOME=/home/stirlingpdfuser \

docker/backend/Dockerfile.ultra-lite

@@ -28,8 +28,7 @@ FROM alpine:3.22.1@sha256:4bcff63911fcb4448bd4fdacec207030997caf25e9bea4045fa6c8
 ARG VERSION_TAG
 
 # Set Environment Variables
-ENV DISABLE_ADDITIONAL_FEATURES=true \
-    HOME=/home/stirlingpdfuser \
+ENV HOME=/home/stirlingpdfuser \
     VERSION_TAG=$VERSION_TAG \
     JAVA_BASE_OPTS="-XX:+UnlockExperimentalVMOptions -XX:MaxRAMPercentage=75 -XX:InitiatingHeapOccupancyPercent=20 -XX:+G1PeriodicGCInvokesConcurrent -XX:G1PeriodicGCInterval=10000 -XX:+UseStringDeduplication -XX:G1PeriodicGCSystemLoadThreshold=70" \
     JAVA_CUSTOM_OPTS="" \