ci: expand backend test matrix and harden build configuration

[Ludy87]

Description of Changes

What was changed

• Expanded the backend task test, format, and format-check commands to run across multiple Gradle/property combinations:
  • default backend build
  • -PbuildWithFrontend=true
  • -PbuildWithFrontend=true -PprototypesMode=true
  • STIRLING_FLAVOR=core
  • STIRLING_FLAVOR=saas
• Updated Gradle build files to reference version values from rootProject.ext consistently across app/common, app/core, app/proprietary, and the root build.gradle.
• Added --enable-native-access=ALL-UNNAMED to test JVM args.
• Adjusted JaCoCo report lookup paths to use the build directory directly and made restart helper compilation read the Java version from the root project.
• Updated the cookie consent stylesheet to align toggle styling with Mantine switch tokens and z-index layering.
• Added .prettierignore for the generated MSW worker file and committed the generated mockServiceWorker.js.
• Updated the SVG-to-PDF test to use a root-relative local file path.
• Marked Docker-dependent Valkey integration tests with disabledWithoutDocker = true so they skip cleanly when Docker is unavailable.

Why the change was made

• To make backend validation more representative of the real build matrix used in this repository.
• To reduce configuration drift by centralizing dependency/version access through the root project.
• To improve CI reliability across platforms and prevent Docker-dependent tests from failing on environments without Docker.
• To keep generated or framework-managed assets from being reformatted unintentionally.
• To align cookie consent UI behavior and appearance more closely with the existing Mantine design system.

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Checklist

General

• I have read the Contribution Guidelines
• I have read the Stirling-PDF Developer Guide (if applicable)
• I have read the How to add new languages to Stirling-PDF (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 (if functionality has heavily changed)
• I have read the section Add New Translation Tags (for new translation tags only)

Translations (if applicable)

• I ran scripts/counter_translation.py

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 run task check to verify linters, typechecks, and tests pass
• I have tested my changes locally. Refer to the Testing Guide for more details.

[stirlingbot]

✅ Backend License Check Passed

All backend dependencies have valid and allowed licenses.

The backend license report has been updated successfully.

[stirlingbot]

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