feat(security): add TOTP-based multi-factor authentication with backend and UI support (#5417)

# Description of Changes

This pull request introduces several improvements and new features
across the authentication and admin data APIs, with a particular focus
on multi-factor authentication (MFA) support and better handling of user
settings. The changes include integrating MFA status into account data
responses, masking sensitive user settings in admin views, and
refactoring code to use more robust user creation methods. Additionally,
there are minor code cleanups and consistency improvements.

### Multi-factor Authentication (MFA) Integration

* Added `mfaEnabled` and `mfaRequired` fields to the `AccountData`
response, populated using the new `MfaService`, to provide clients with
MFA status information for users.
[[1]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R430-R431)
[[2]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R72)
[[3]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L83-R86)
[[4]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R98)
[[5]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R574-R575)

### User Settings Handling and Security

* Admin settings API now returns user settings for each user, with the
`mfaSecret` field masked to protect sensitive information. This is
achieved by fetching settings via `findByIdWithSettings` and
copying/masking the relevant field before returning.
[[1]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R252-R259)
[[2]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L302-R322)
[[3]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R378)
[[4]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1R563)

### Refactoring and Code Consistency

* Refactored user creation in `InitialSecuritySetup` to use the
`SaveUserRequest` builder and `saveUserCore` for better maintainability
and clarity, replacing direct calls to `saveUser`.
[[1]](diffhunk://#diff-0c7960a6283a07c4905ac9785b2820b412574c9f86918ada30caba0356d34850R22)
[[2]](diffhunk://#diff-0c7960a6283a07c4905ac9785b2820b412574c9f86918ada30caba0356d34850L116-R124)
[[3]](diffhunk://#diff-0c7960a6283a07c4905ac9785b2820b412574c9f86918ada30caba0356d34850L130-R144)
[[4]](diffhunk://#diff-0c7960a6283a07c4905ac9785b2820b412574c9f86918ada30caba0356d34850L140-R160)
* Standardized checks for internal team membership by comparing with
`TeamService.INTERNAL_TEAM_NAME` on the left side for consistency.
[[1]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L267-R273)
[[2]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L332-R351)
[[3]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L421-R443)
[[4]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L449-R471)
[[5]](diffhunk://#diff-2ead183708656f2c6894b28457623820c83b1ed4b0814533caa0e8f0dd6fbcd1L462-R485)

### API and DTO Changes

* Changed the login API to accept `UsernameAndPassMfa` instead of
`UsernameAndPass`, paving the way for MFA code support in authentication
requests.
[[1]](diffhunk://#diff-9ca4f9246abe79368552264e2e18d7ed039e084c70c0794eb02cfd1b75fbd8a8L30-R41)
[[2]](diffhunk://#diff-9ca4f9246abe79368552264e2e18d7ed039e084c70c0794eb02cfd1b75fbd8a8L61-R71)
* Updated import statements and controller dependencies to include new
DTOs and services related to MFA.
[[1]](diffhunk://#diff-9ca4f9246abe79368552264e2e18d7ed039e084c70c0794eb02cfd1b75fbd8a8L14-R19)
[[2]](diffhunk://#diff-9ca4f9246abe79368552264e2e18d7ed039e084c70c0794eb02cfd1b75fbd8a8R56-R57)

These updates improve security, prepare the system for MFA rollout, and
make admin and authentication APIs more robust and informative.

---

## 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.

---------

Co-authored-by: Copilot <[email protected]>

frontend/src-tauri/src/commands/auth.rs

@@ -33,15 +33,20 @@ fn get_keyring_entry() -> Result<Entry, String> {
 
 #[tauri::command]
 pub async fn save_auth_token(_app_handle: AppHandle, token: String) -> Result<(), String> {
-    if token.is_empty() {
+    let trimmed = token.trim();
+    if trimmed.is_empty() {
         log::warn!("Attempted to save empty auth token");
         return Err("Token cannot be empty".to_string());
     }
 
     let entry = get_keyring_entry()?;
 
+    if trimmed.len() != token.len() {
+        log::debug!("Auth token had surrounding whitespace; storing trimmed token");
+    }
+
     entry
-        .set_password(&token)
+        .set_password(trimmed)
         .map_err(|e| {
             log::error!("Failed to set password in keyring: {}", e);
             format!("Failed to save token to keyring: {}", e)
@@ -50,7 +55,7 @@ pub async fn save_auth_token(_app_handle: AppHandle, token: String) -> Result<()
     // Verify the save worked
     match entry.get_password() {
         Ok(retrieved_token) => {
-            if retrieved_token != token {
+            if retrieved_token != trimmed {
                 log::error!("Token verification failed: Retrieved token doesn't match");
                 return Err("Token verification failed after save".to_string());
             }
@@ -201,6 +206,7 @@ pub async fn login(
     server_url: String,
     username: String,
     password: String,
+    mfa_code: Option<String>,
     supabase_key: String,
     saas_server_url: String,
 ) -> Result<LoginResponse, String> {
@@ -272,12 +278,22 @@ pub async fn login(
         let login_url = format!("{}/api/v1/auth/login", server_url.trim_end_matches('/'));
         log::debug!("Spring Boot login URL: {}", login_url);
 
+        let mut payload = serde_json::json!({
+            "username": username,
+            "password": password,
+        });
+
+        if let Some(code) = mfa_code
+            .as_ref()
+            .map(|c| c.trim())
+            .filter(|c| !c.is_empty())
+        {
+            payload["mfaCode"] = serde_json::Value::String(code.to_string());
+        }
+
         let response = client
             .post(&login_url)
-            .json(&serde_json::json!({
-                "username": username,
-                "password": password,
-            }))
+            .json(&payload)
             .send()
             .await
             .map_err(|e| format!("Network error: {}", e))?;
@@ -292,6 +308,19 @@ pub async fn login(
                 .unwrap_or_else(|_| "Unknown error".to_string());
             log::error!("Spring Boot login failed with status {}: {}", status, error_text);
 
+            if let Ok(error_json) = serde_json::from_str::<serde_json::Value>(&error_text) {
+                let error_code = error_json
+                    .get("error")
+                    .and_then(|value| value.as_str())
+                    .map(|value| value.to_string());
+
+                if let Some(code) = error_code {
+                    if code == "mfa_required" || code == "invalid_mfa_code" {
+                        return Err(code);
+                    }
+                }
+            }
+
             return Err(if status.as_u16() == 401 {
                 "Invalid username or password".to_string()
             } else if status.as_u16() == 403 {