JWT Authentication (#3921)

This PR introduces JWT (JSON Web Token) authentication for Stirling-PDF,
allowing for stateless authentication capabilities alongside the
existing session-based authentication system.

### Key Features & Changes

  JWT Authentication System
- Core Service: JwtService.java - Token generation, validation, and
cookie management
- Authentication Filter: JwtAuthenticationFilter.java - Request
interceptor for JWT validation
- Key Management: KeyPersistenceService.java +
KeyPairCleanupService.java - RSA key rotation and persistence
  - Frontend: jwt-init.js - Client-side JWT handling and URL cleanup

  Security Integration
- SAML2: JwtSaml2AuthenticationRequestRepository.java - JWT-backed SAML
request storage
- OAuth2: Updated CustomAuthenticationSuccessHandler. java,
CustomOAuth2AuthenticationSuccessHandler.java &
CustomSaml2AuthenticationSuccessHandler.java for JWT integration
- Configuration: Enhanced SecurityConfiguration.java with JWT filter
chain

  Infrastructure
  - Caching: CacheConfig.java - Caffeine cache for JWT keys
  - Database: New JwtVerificationKey.java entity for key storage
- Error Handling: JwtAuthenticationEntryPoint.java for unauthorized
access

### Challenges Encountered

- Configured SecurityConfiguration to use either
`UsernamePasswordAuthenticationFilter` or `JWTAuthenticationFilter`
based on whether JWTs are enabled to prevent the former intercepting
requests while in stateless mode.
- Removed the `.defaultSuccessUrl("/")` from login configuration as its
inclusion was preventing overriding the use of the
`CustomAuthenticationSuccessHandler` and preventing proper
authentication flows.
---

## 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/devGuide/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/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [x] 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)
- [x] 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)

- [x] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)
<img width="599" height="515" alt="Screenshot 2025-07-10 at 13 35 56"
src="https://github.com/user-attachments/assets/4126b752-ad0d-4ffa-b295-6714c43381e1"
/>

<img width="392" height="376" alt="Screenshot 2025-07-10 at 13 36 10"
src="https://github.com/user-attachments/assets/c681bc43-68ff-4934-8245-d544e2ad7b9c"
/>

<img width="1870" height="986" alt="eb750e8c3954fc47b2dd2e6e76ddb7d5"
src="https://github.com/user-attachments/assets/fca9b23d-b0b6-4884-8a26-98a441b641ef"
/>

<img width="1299" height="702" alt="Screenshot 2025-07-10 at 13 30 57"
src="https://github.com/user-attachments/assets/9415d8bf-fac4-4d38-8c3a-985d043d1076"
/>

### Testing (if applicable)

- [x] 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.

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ludy <Ludy87@users.noreply.github.com>
Co-authored-by: EthanHealy01 <80844253+EthanHealy01@users.noreply.github.com>
Co-authored-by: Ethan <ethan@MacBook-Pro.local>
Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

app/common/src/main/java/stirling/software/common/configuration/AppConfig.java

@@ -8,6 +8,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Properties;
 import java.util.function.Predicate;
+import java.util.stream.Stream;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -51,6 +52,14 @@ public class AppConfig {
     @Value("${server.port:8080}")
     private String serverPort;
 
+    @Value("${v2}")
+    public boolean v2Enabled;
+
+    @Bean
+    public boolean v2Enabled() {
+        return v2Enabled;
+    }
+
     @Bean
     @ConditionalOnProperty(name = "system.customHTMLFiles", havingValue = "true")
     public SpringTemplateEngine templateEngine(ResourceLoader resourceLoader) {
@@ -120,7 +129,7 @@ public class AppConfig {
     public boolean rateLimit() {
         String rateLimit = System.getProperty("rateLimit");
         if (rateLimit == null) rateLimit = System.getenv("rateLimit");
-        return (rateLimit != null) ? Boolean.valueOf(rateLimit) : false;
+        return Boolean.parseBoolean(rateLimit);
     }
 
     @Bean(name = "RunningInDocker")
@@ -140,8 +149,8 @@ public class AppConfig {
         if (!Files.exists(mountInfo)) {
             return true;
         }
-        try {
-            return Files.lines(mountInfo).anyMatch(line -> line.contains(" /configs "));
+        try (Stream<String> lines = Files.lines(mountInfo)) {
+            return lines.anyMatch(line -> line.contains(" /configs "));
         } catch (IOException e) {
             return false;
         }

app/common/src/main/java/stirling/software/common/configuration/InstallationPathConfig.java

@@ -25,6 +25,7 @@ public class InstallationPathConfig {
     private static final String STATIC_PATH;
     private static final String TEMPLATES_PATH;
     private static final String SIGNATURES_PATH;
+    private static final String PRIVATE_KEY_PATH;
 
     static {
         BASE_PATH = initializeBasePath();
@@ -45,6 +46,7 @@ public class InstallationPathConfig {
         STATIC_PATH = CUSTOM_FILES_PATH + "static" + File.separator;
         TEMPLATES_PATH = CUSTOM_FILES_PATH + "templates" + File.separator;
         SIGNATURES_PATH = CUSTOM_FILES_PATH + "signatures" + File.separator;
+        PRIVATE_KEY_PATH = CONFIG_PATH + "db" + File.separator + "keys" + File.separator;
     }
 
     private static String initializeBasePath() {
@@ -120,4 +122,8 @@ public class InstallationPathConfig {
     public static String getSignaturesPath() {
         return SIGNATURES_PATH;
     }
+
+    public static String getPrivateKeyPath() {
+        return PRIVATE_KEY_PATH;
+    }
 }

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

@@ -119,6 +119,7 @@ public class ApplicationProperties {
         private long loginResetTimeMinutes;
         private String loginMethod = "all";
         private String customGlobalAPIKey;
+        private Jwt jwt = new Jwt();
 
         public Boolean isAltLogin() {
             return saml2.getEnabled() || oauth2.getEnabled();
@@ -298,6 +299,15 @@ public class ApplicationProperties {
                 }
             }
         }
+
+        @Data
+        public static class Jwt {
+            private boolean enableKeystore = true;
+            private boolean enableKeyRotation = false;
+            private boolean enableKeyCleanup = true;
+            private int keyRetentionDays = 7;
+            private boolean secureCookie;
+        }
     }
 
     @Data

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

@@ -14,8 +14,10 @@ public class RequestUriUtils {
                 || requestURI.startsWith(contextPath + "/images/")
                 || requestURI.startsWith(contextPath + "/public/")
                 || requestURI.startsWith(contextPath + "/pdfjs/")
+                || requestURI.startsWith(contextPath + "/pdfjs-legacy/")
                 || requestURI.startsWith(contextPath + "/login")
                 || requestURI.startsWith(contextPath + "/error")
+                || requestURI.startsWith(contextPath + "/favicon")
                 || requestURI.endsWith(".svg")
                 || requestURI.endsWith(".png")
                 || requestURI.endsWith(".ico")