feat(review): add integration review APIs and adjust UI

Add client-side wrappers for creating integration review requests and
for listing repository branches, and wire native command imports so the
app can call those integration endpoints. Update the review center UI to
include a create-review dialog import and refine table and provider
button layout for improved spacing and readability.

- Add wrappers for create review requests and branch listing
- Wire native integration imports and prepare the create-review dialog
- Adjust table sizing and provider button layout for better spacing

src/lib/git.ts

@@ -702,3 +702,11 @@ export function addIntegrationIssueComment(provider: GitIntegrationProvider, bas
 export function closeIntegrationIssue(provider: GitIntegrationProvider, baseUrl: string, username: string, token: string, repository: string, number: number): Promise<string> {
   return invoke("close_integration_issue", { provider, baseUrl, username, token, repository, number });
 }
+
+export function createIntegrationReviewRequest(provider: GitIntegrationProvider, baseUrl: string, username: string, token: string, repository: GitIntegrationRepository, sourceBranch: string, targetBranch: string, title: string, description: string): Promise<IntegrationReviewRequest> {
+  return invoke("create_integration_review_request", { provider, baseUrl, username, token, repository, sourceBranch, targetBranch, title, description });
+}
+
+export function listIntegrationRepositoryBranches(provider: GitIntegrationProvider, baseUrl: string, username: string, token: string, repository: GitIntegrationRepository): Promise<{branches: string[]; defaultBranch: string}> {
+  return invoke("list_integration_repository_branches", {provider, baseUrl, username, token, repository});
+}