New common module (#3573)

# Description of Changes

Introduced a new `common` module for shared libs and commonly used
classes. See the screenshot below for the file structure and classes
that have been moved.

---
<img width="452" alt="Screenshot 2025-05-22 at 11 46 56"
src="https://github.com/user-attachments/assets/c9badabc-48f9-4079-b83e-7cfde0fb840f"
/>
<img width="470" alt="Screenshot 2025-05-22 at 11 47 30"
src="https://github.com/user-attachments/assets/e8315b09-2e78-4c50-b9de-4dd9b9b0ecb1"
/>

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [x] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] 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/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [x] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

build.gradle

@@ -413,13 +413,14 @@ configurations.all {
     // Exclude Tomcat
     exclude group: "org.springframework.boot", module: "spring-boot-starter-tomcat"
 }
+
 dependencies {
+    implementation project(':common')
 
     //tmp for security bumps
     implementation 'ch.qos.logback:logback-core:1.5.18'
     implementation 'ch.qos.logback:logback-classic:1.5.18'
 
-
     // Exclude vulnerable BouncyCastle version used in tableau
     configurations.all {
         exclude group: 'org.bouncycastle', module: 'bcpkix-jdk15on'
@@ -448,8 +449,6 @@ dependencies {
 
 
     if (System.getenv("DOCKER_ENABLE_SECURITY") != "false") {
-
-	    implementation 'org.springframework.boot:spring-boot-starter-actuator'
 	    implementation 'io.micrometer:micrometer-registry-prometheus'
 
         implementation "org.springframework.boot:spring-boot-starter-security:$springBootVersion"
@@ -545,7 +544,6 @@ dependencies {
 
   // Mockito (core)
     testImplementation 'org.mockito:mockito-core:5.18.0'
-
     testRuntimeOnly 'org.mockito:mockito-inline:5.2.0'
 }