Add audit system, invite links, and usage analytics (#4749)

# Description of Changes

New Features
Audit System: Complete audit logging with dashboard, event tracking, and
export capabilities

Invite Links: Secure invite system with email notifications and
expiration

Usage Analytics: Endpoint usage statistics and visualization

License Management: User counting with grandfathering and license
enforcement
## 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)

### 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.

---------

Co-authored-by: James Brunton <jbrunton96@gmail.com>

app/common/src/main/java/stirling/software/common/model/ApplicationProperties.java

@@ -368,6 +368,10 @@ public class ApplicationProperties {
         private TempFileManagement tempFileManagement = new TempFileManagement();
         private DatabaseBackup databaseBackup = new DatabaseBackup();
         private List<String> corsAllowedOrigins = new ArrayList<>();
+        private String
+                frontendUrl; // Base URL for frontend (used for invite links, etc.). If not set,
+
+        // falls back to backend URL.
 
         public boolean isAnalyticsEnabled() {
             return this.getEnableAnalytics() != null && this.getEnableAnalytics();
@@ -556,6 +560,7 @@ public class ApplicationProperties {
     public static class Mail {
         private boolean enabled;
         private boolean enableInvites = false;
+        private int inviteLinkExpiryHours = 72; // Default: 72 hours (3 days)
         private String host;
         private int port;
         private String username;

app/common/src/main/java/stirling/software/common/util/JarPathUtil.java

@@ -43,26 +43,45 @@ public class JarPathUtil {
     }
 
     /**
-     * Gets the path to the restart-helper.jar file Expected to be in the same directory as the main
-     * JAR
+     * Gets the path to the restart-helper.jar file. Checks multiple possible locations: 1. Same
+     * directory as the main JAR (production deployment) 2. ./build/libs/restart-helper.jar
+     * (development build) 3. app/common/build/libs/restart-helper.jar (multi-module build)
      *
      * @return Path to restart-helper.jar, or null if not found
      */
     public static Path restartHelperJar() {
         Path appJar = currentJar();
-        if (appJar == null) {
-            return null;
+
+        // Define possible locations to check (in order of preference)
+        Path[] possibleLocations = new Path[4];
+
+        // Location 1: Same directory as main JAR (production)
+        if (appJar != null) {
+            possibleLocations[0] = appJar.getParent().resolve("restart-helper.jar");
         }
 
-        Path helperJar = appJar.getParent().resolve("restart-helper.jar");
+        // Location 2: ./build/libs/ (development build)
+        possibleLocations[1] = Paths.get("build", "libs", "restart-helper.jar").toAbsolutePath();
 
-        if (Files.isRegularFile(helperJar)) {
-            log.debug("Restart helper JAR located at: {}", helperJar);
-            return helperJar;
-        } else {
-            log.warn("Restart helper JAR not found at: {}", helperJar);
-            return null;
+        // Location 3: app/common/build/libs/ (multi-module build)
+        possibleLocations[2] =
+                Paths.get("app", "common", "build", "libs", "restart-helper.jar").toAbsolutePath();
+
+        // Location 4: Current working directory
+        possibleLocations[3] = Paths.get("restart-helper.jar").toAbsolutePath();
+
+        // Check each location
+        for (Path location : possibleLocations) {
+            if (location != null && Files.isRegularFile(location)) {
+                log.info("Restart helper JAR found at: {}", location);
+                return location;
+            } else if (location != null) {
+                log.debug("Restart helper JAR not found at: {}", location);
+            }
         }
+
+        log.warn("Restart helper JAR not found in any expected location");
+        return null;
     }
 
     /**

app/common/src/main/java/stirling/software/common/util/RequestUriUtils.java

@@ -76,6 +76,8 @@ public class RequestUriUtils {
                 || trimmedUri.startsWith("/api/v1/auth/refresh")
                 || trimmedUri.startsWith("/api/v1/auth/logout")
                 || trimmedUri.startsWith("/v1/api-docs")
+                || trimmedUri.startsWith("/api/v1/invite/validate")
+                || trimmedUri.startsWith("/api/v1/invite/accept")
                 || trimmedUri.contains("/v1/api-docs");
     }
 }

app/common/src/main/java/stirling/software/common/util/YamlHelper.java

@@ -10,6 +10,7 @@ import java.util.Arrays;
 import java.util.Deque;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
@@ -135,6 +136,17 @@ public class YamlHelper {
                 } else if ("true".equals(newValue) || "false".equals(newValue)) {
                     newValueNode =
                             new ScalarNode(Tag.BOOL, String.valueOf(newValue), ScalarStyle.PLAIN);
+                } else if (newValue instanceof Map<?, ?> map) {
+                    // Handle Map objects - convert to MappingNode
+                    List<NodeTuple> mapTuples = new ArrayList<>();
+                    for (Map.Entry<?, ?> entry : map.entrySet()) {
+                        ScalarNode mapKeyNode =
+                                new ScalarNode(
+                                        Tag.STR, String.valueOf(entry.getKey()), ScalarStyle.PLAIN);
+                        Node mapValueNode = convertValueToNode(entry.getValue());
+                        mapTuples.add(new NodeTuple(mapKeyNode, mapValueNode));
+                    }
+                    newValueNode = new MappingNode(Tag.MAP, mapTuples, FlowStyle.BLOCK);
                 } else if (newValue instanceof List<?> list) {
                     List<Node> sequenceNodes = new ArrayList<>();
                     for (Object item : list) {
@@ -458,6 +470,43 @@ public class YamlHelper {
         return isInteger(object) || isShort(object) || isByte(object) || isLong(object);
     }
 
+    /**
+     * Converts a Java value to a YAML Node.
+     *
+     * @param value The value to convert.
+     * @return The corresponding YAML Node.
+     */
+    private Node convertValueToNode(Object value) {
+        if (value == null) {
+            return new ScalarNode(Tag.NULL, "null", ScalarStyle.PLAIN);
+        } else if (isAnyInteger(value)) {
+            return new ScalarNode(Tag.INT, String.valueOf(value), ScalarStyle.PLAIN);
+        } else if (isFloat(value)) {
+            Object floatValue = Float.valueOf(String.valueOf(value));
+            return new ScalarNode(Tag.FLOAT, String.valueOf(floatValue), ScalarStyle.PLAIN);
+        } else if (value instanceof Boolean || "true".equals(value) || "false".equals(value)) {
+            return new ScalarNode(Tag.BOOL, String.valueOf(value), ScalarStyle.PLAIN);
+        } else if (value instanceof Map<?, ?> map) {
+            // Recursively handle nested maps
+            List<NodeTuple> mapTuples = new ArrayList<>();
+            for (Map.Entry<?, ?> entry : map.entrySet()) {
+                ScalarNode mapKeyNode =
+                        new ScalarNode(Tag.STR, String.valueOf(entry.getKey()), ScalarStyle.PLAIN);
+                Node mapValueNode = convertValueToNode(entry.getValue());
+                mapTuples.add(new NodeTuple(mapKeyNode, mapValueNode));
+            }
+            return new MappingNode(Tag.MAP, mapTuples, FlowStyle.BLOCK);
+        } else if (value instanceof List<?> list) {
+            List<Node> sequenceNodes = new ArrayList<>();
+            for (Object item : list) {
+                sequenceNodes.add(convertValueToNode(item));
+            }
+            return new SequenceNode(Tag.SEQ, sequenceNodes, FlowStyle.FLOW);
+        } else {
+            return new ScalarNode(Tag.STR, String.valueOf(value), ScalarStyle.PLAIN);
+        }
+    }
+
     /**
      * Copies comments from an old node to a new one.
      *