removal of old java desktop + workspace change in tauri (#5459)

# Description of Changes

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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)

### 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/Dockerfile.unified

@@ -31,7 +31,6 @@ COPY . .
 
 # Build server-only JAR (no frontend, includes security features controlled by DOCKER_ENABLE_SECURITY at runtime)
 RUN DISABLE_ADDITIONAL_FEATURES=false \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # Stage 3: Final unified image

docker/Dockerfile.unified-lite

@@ -30,7 +30,6 @@ WORKDIR /app
 COPY . .
 
 RUN DISABLE_ADDITIONAL_FEATURES=true \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # Stage 3: Final unified ultra-lite image

docker/backend/Dockerfile

@@ -25,7 +25,6 @@ COPY . .
 
 # 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
 
 # ========================================

docker/backend/Dockerfile.fat

@@ -25,7 +25,6 @@ COPY . .
 
 # 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
 
 # ========================================

docker/backend/Dockerfile.ultra-lite

@@ -21,7 +21,6 @@ COPY . .
 
 # Build the application with DISABLE_ADDITIONAL_FEATURES=true
 RUN DISABLE_ADDITIONAL_FEATURES=true \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # ========================================

docker/embedded/Dockerfile

@@ -32,7 +32,6 @@ COPY . .
 
 # Build JAR with embedded frontend (includes security features controlled at runtime)
 RUN DISABLE_ADDITIONAL_FEATURES=false \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -PbuildWithFrontend=true -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # Stage 2: Runtime image based on Debian stable-slim

docker/embedded/Dockerfile.fat

@@ -32,7 +32,6 @@ COPY . .
 
 # Build JAR with embedded frontend (includes security features controlled at runtime)
 RUN DISABLE_ADDITIONAL_FEATURES=false \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -PbuildWithFrontend=true -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # Stage 2: Runtime image based on Debian stable-slim

docker/embedded/Dockerfile.ultra-lite

@@ -32,7 +32,6 @@ COPY . .
 
 # Build ultra-lite JAR with embedded frontend (minimal features)
 RUN DISABLE_ADDITIONAL_FEATURES=true \
-    STIRLING_PDF_DESKTOP_UI=false \
     ./gradlew clean build -PbuildWithFrontend=true -x spotlessApply -x spotlessCheck -x test -x sonarqube
 
 # Stage 2: Runtime image