feat(backlog): add branchName support to apply handler and UI components

- Updated apply handler to accept an optional branchName from the request body.
- Modified BoardView and BacklogPlanDialog components to pass currentBranch to the apply API.
- Enhanced ElectronAPI and HttpApiClient to include branchName in the apply method.

This change allows users to specify a branch when applying backlog plans, improving flexibility in feature management.

apps/ui/src/lib/http-api-client.ts

@@ -2202,9 +2202,10 @@ export class HttpApiClient implements ElectronAPI {
           removedDependencies: string[];
           addedDependencies: string[];
         }>;
-      }
+      },
+      branchName?: string
     ): Promise<{ success: boolean; appliedChanges?: string[]; error?: string }> =>
-      this.post('/api/backlog-plan/apply', { projectPath, plan }),
+      this.post('/api/backlog-plan/apply', { projectPath, plan, branchName }),
 
     onEvent: (callback: (data: unknown) => void): (() => void) => {
       return this.subscribeToEvent('backlog-plan:event', callback as EventCallback);