chore(ci): enable Gradle dependency caching across GitHub workflows (#5400)

# Description of Changes

This pull request updates the CI/CD workflows and Gradle configuration
to improve build reproducibility, security, and external dependency
management. The main changes include standardizing Gradle setup across
workflows, securely injecting Maven credentials, and enabling Gradle
build caching. There are also minor improvements to dependency version
management and plugin repository configuration.

**CI/CD Workflow Improvements:**

- Standardized Gradle setup across all GitHub Actions workflows by
explicitly adding a `Setup Gradle` step using
`gradle/actions/[email protected]` and specifying Gradle version 8.14.
This replaces previous usages and ensures consistency.
[[1]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R71-R81)
[[2]](diffhunk://#diff-8d23782ae5caff72d55828bb25814854f5f2523f299d7dbcda4a3537dd84c5c3L157-R176)
[[3]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R134-R144)
[[4]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R206-R216)
[[5]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R260-R264)
[[6]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R331-R341)
[[7]](diffhunk://#diff-3c0f521958c53ad27c967692b4d5480ead136acb33622ee97d39df814b1b202eR339-R351)
[[8]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bL53-R54)
[[9]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bL121-R127)
[[10]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bR206-R217)
[[11]](diffhunk://#diff-6a2e9fb077e57351f4a7e10d03b114e256298babdf06e7e7ae666781a5cf36a1R60-R70)
[[12]](diffhunk://#diff-62dcbe64a950b4efb54d691e1e87451a8cd535400aa9ea1e40893de5b57cd73bL45-R46)
[[13]](diffhunk://#diff-76056236de05155107f6a660f1e3956059e37338011b8f0e72188afcb9b17b6fL46-R56)
[[14]](diffhunk://#diff-fd60dc2adec58c1005c4e4164e9c24362fd6082fd3ab0403e54d276d9835fa6eL42-R65)
[[15]](diffhunk://#diff-b34ab107dd4bc92075b2e89b6f16e4a2813e267ca7c2afebdb1931a0a3900d5aR102-R114)
[[16]](diffhunk://#diff-98b618771a57e1758961359ecacbac2cff7cfef29aa021c3bc294ae926c4ce5bL47-R51)

- Enabled Gradle build cache (`--build-cache`) for all build-related
commands in workflows, improving build performance and consistency. Also
removed unnecessary `clean` commands before builds to further optimize
workflow times.
[[1]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R71-R81)
[[2]](diffhunk://#diff-8d23782ae5caff72d55828bb25814854f5f2523f299d7dbcda4a3537dd84c5c3L157-R176)
[[3]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R134-R144)
[[4]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R206-R216)
[[5]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R331-R341)
[[6]](diffhunk://#diff-3c0f521958c53ad27c967692b4d5480ead136acb33622ee97d39df814b1b202eR339-R351)
[[7]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bL134-R144)
[[8]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bR206-R217)
[[9]](diffhunk://#diff-6a2e9fb077e57351f4a7e10d03b114e256298babdf06e7e7ae666781a5cf36a1R60-R70)
[[10]](diffhunk://#diff-76056236de05155107f6a660f1e3956059e37338011b8f0e72188afcb9b17b6fL46-R56)
[[11]](diffhunk://#diff-fd60dc2adec58c1005c4e4164e9c24362fd6082fd3ab0403e54d276d9835fa6eL42-R65)
[[12]](diffhunk://#diff-b34ab107dd4bc92075b2e89b6f16e4a2813e267ca7c2afebdb1931a0a3900d5aR102-R114)
[[13]](diffhunk://#diff-98b618771a57e1758961359ecacbac2cff7cfef29aa021c3bc294ae926c4ce5bL47-R51)

**Security and Dependency Management:**

- Injected Maven credentials (`MAVEN_USER`, `MAVEN_PASSWORD`,
`MAVEN_PUBLIC_URL`) as environment variables in all relevant workflow
steps, supporting secure access to private or custom Maven repositories.
[[1]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R71-R81)
[[2]](diffhunk://#diff-8d23782ae5caff72d55828bb25814854f5f2523f299d7dbcda4a3537dd84c5c3L157-R176)
[[3]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R134-R144)
[[4]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R206-R216)
[[5]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R290-R293)
[[6]](diffhunk://#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R331-R341)
[[7]](diffhunk://#diff-3c0f521958c53ad27c967692b4d5480ead136acb33622ee97d39df814b1b202eR339-R351)
[[8]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bR66-R69)
[[9]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bL134-R144)
[[10]](diffhunk://#diff-895b214ee023c8c26048a2a3b946cfb1ebc4f26fbc8a9c2fa54b77c12e763b6bR281-R283)
[[11]](diffhunk://#diff-62dcbe64a950b4efb54d691e1e87451a8cd535400aa9ea1e40893de5b57cd73bR57-R60)
[[12]](diffhunk://#diff-76056236de05155107f6a660f1e3956059e37338011b8f0e72188afcb9b17b6fR73-R76)
[[13]](diffhunk://#diff-fd60dc2adec58c1005c4e4164e9c24362fd6082fd3ab0403e54d276d9835fa6eL42-R65)
[[14]](diffhunk://#diff-b34ab107dd4bc92075b2e89b6f16e4a2813e267ca7c2afebdb1931a0a3900d5aR178-R180)
[[15]](diffhunk://#diff-98b618771a57e1758961359ecacbac2cff7cfef29aa021c3bc294ae926c4ce5bL47-R51)

- Added a `pluginManagement` block in `settings.gradle` to allow Gradle
plugins to be resolved from a custom Maven repository if specified by
environment variables, increasing flexibility for plugin sourcing.

**Build and Dependency Versioning:**

- Updated `app/proprietary/build.gradle` to use the
`bouncycastleVersion` variable for the Bouncy Castle dependency version,
improving maintainability and consistency of dependency versioning.

**Workflow Trigger Improvements:**

- Expanded the file path triggers in
`.github/workflows/sync_files_v2.yml` to include additional Gradle build
files, ensuring the workflow runs when any core build files are changed.

---

## 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.

Author: Ludy87

app/proprietary/build.gradle

@@ -1,5 +1,5 @@
 repositories {
-    maven { url = "https://build.shibboleth.net/maven/releases" }
+    maven { url "https://build.shibboleth.net/maven/releases" }
 }
 
 ext {