feat(integrations): add create integration review request API and UI

Add a new Tauri command and front-end flow to create PRs/MRs.
The backend builds and validates provider-specific payloads and
endpoints, sends creation requests, and parses responses into the
app's review model. A Svelte dialog and a JS wrapper wire the UI to the
command so users can create requests from the Review Center.

- Implement provider payload and endpoint logic with unit tests
- Expose create_integration_review_request as a Tauri command
- Add CreateReviewDialog UI and integrate a creation button in Review Center

src-tauri/src/main.rs

@@ -34,7 +34,7 @@ use git::{
     unstage_files, untrack_paths, update_remote,
 };
 use integrations::{
-    add_integration_review_comment, get_integration_review_details, list_integration_repositories, list_integration_review_requests, open_in_browser,
+    create_integration_review_request, add_integration_review_comment, get_integration_review_details, list_integration_repositories, list_integration_review_requests, open_in_browser,
     run_integration_review_action,
 };
 use std::path::{Path, PathBuf};
@@ -437,6 +437,7 @@ async fn main() {
             cred_load,
             cred_save,
             cred_delete,
+            create_integration_review_request,
             list_integration_repositories,
             list_integration_review_requests,
             get_integration_review_details,