deps: upgrade mwiede JSch to 2.28.6 and adapt SFTP password handling (#7496)

# Description of Changes

This PR replaces #7490 and upgrades `com.github.mwiede:jsch` from
`0.2.23` to `2.28.6`.

In addition to the dependency bump from the original Dependabot PR, this
PR includes the required compatibility adjustment for SFTP password
authentication:

- Updated `jschVersion` in `build.gradle` from `0.2.23` to `2.28.6`.
- Updated `SftpFileClient` to pass the configured password to JSch as
UTF-8 encoded bytes instead of using the `String` overload.
- Preserved the existing SFTP connection and host-key verification
behavior.
- Addresses the API compatibility changes introduced by the newer JSch
version that prevented the dependency upgrade from being used unchanged.

This supersedes #7490

---

## 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/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 run `task check` to verify linters, typechecks, and tests
pass
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Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

app/proprietary/src/main/java/stirling/software/proprietary/policy/network/SftpFileClient.java

@@ -65,7 +65,7 @@ final class SftpFileClient implements RemoteFileClient {
             }
             Session session = jsch.getSession(config.username(), config.host(), config.port());
             if (config.password() != null) {
-                session.setPassword(config.password());
+                session.setPassword(config.password().getBytes(StandardCharsets.UTF_8));
             }
             if (config.hostKeyFingerprint() != null) {
                 // Pinned key: only the configured fingerprint is ever accepted.

build.gradle

@@ -45,7 +45,7 @@ ext {
     jpdfiumVersion = "1.0.4"
     jwtVersion = "0.13.0"
     awsSdkVersion = "2.44.12"
-    jschVersion = "0.2.23"
+    jschVersion = "2.28.6"
     commonsNetVersion = "3.11.1"
     smbjVersion = "0.14.0"
     tinkVersion = "1.23.0"