feat(integrations): add review fetching and Linux keyring support

Add a cross-provider Review Center and improve credential handling.
Backend integrations fetch and normalize PRs from GitHub, GitLab,
Gitea, and Azure DevOps with improved timeouts and parsing. Credentials
now use a global lock and support secret-tool on Linux to avoid races.

- Normalize review data across providers (GitHub/GitLab/Gitea/Azure)
- Serialize credential access with OnceLock and use secret-tool on Linux
- Add frontend ReviewCenter component and related UI updates

src-tauri/src/main.rs

@@ -33,7 +33,10 @@ use git::{
     stash_apply, stash_drop, stash_pop, stash_push, undo_last_commit, unlock_worktree,
     unstage_files, untrack_paths, update_remote,
 };
-use integrations::list_integration_repositories;
+use integrations::{
+    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};
 use std::sync::Mutex;
 use tauri::{Emitter, Manager};
@@ -435,6 +438,11 @@ async fn main() {
             cred_save,
             cred_delete,
             list_integration_repositories,
+            list_integration_review_requests,
+            get_integration_review_details,
+            add_integration_review_comment,
+            run_integration_review_action,
+            open_in_browser,
             set_sync_badge,
             close_splashscreen,
             set_telemetry_enabled,