feat(api): add comprehensive repository management API endpoints

- Introduce new repo module with complete repository functionality
- Add endpoints for repository CRUD operations (create, get, update, archive, delete)
- Implement branch management with create, list, delete and protection features
- Add tag management with create, list and delete operations
- Include release management with create, update and delete capabilities
- Support repository forking with sync functionality
- Implement starring and watching mechanisms for repositories
- Add member management with roles and invitations
- Provide deploy key management for CI/CD integration
- Create webhook management for external integrations
- Implement branch protection rules with approval requirements
- Add commit status and comment functionality for code reviews
- Include merge checking logic for pull requests
- Register all new endpoints in OpenAPI documentation
- Configure routes to handle new repository-specific paths

api/repo/set_default_branch.rs

@@ -0,0 +1,58 @@
+use actix_web::{web, HttpResponse};
+use serde::Deserialize;
+use utoipa::IntoParams;
+
+use crate::api::response::{ApiResponse, ApiErrorResponse};
+use crate::error::AppError;
+use crate::service::AppService;
+use crate::session::Session;
+
+#[derive(Debug, Deserialize, IntoParams)]
+pub struct PathParams {
+    /// Workspace name (unique identifier)
+    pub workspace_name: String,
+    /// Repository name (unique within the workspace)
+    pub repo_name: String,
+    /// Branch ID (UUID)
+    pub branch_id: uuid::Uuid,
+}
+
+/// Set default branch
+///
+/// Sets a branch as the repository's default branch. The default branch is used for:
+/// - New pull requests base branch
+/// - Repository cloning
+/// - New branch creation base
+/// 
+/// Requires Admin role or higher in the repository.
+/// 
+/// Returns success message on completion.
+#[utoipa::path(
+    put,
+    path = "/api/v1/workspaces/{workspace_name}/repos/{repo_name}/branches/{branch_id}/default",
+    tag = "Repos",
+    operation_id = "repoSetDefaultBranch",
+    params(PathParams),
+    responses(
+        (status = 200, description = "Default branch set successfully. All new operations will use this branch as the default.", body = ApiResponse<String>),
+        (status = 401, description = "Authentication required or session expired", body = ApiErrorResponse),
+        (status = 403, description = "Insufficient permissions (requires Admin role or higher)", body = ApiErrorResponse),
+        (status = 404, description = "Repository, workspace, or branch not found", body = ApiErrorResponse),
+        (status = 500, description = "Internal server error", body = ApiErrorResponse),
+    ),
+    security(
+        ("session_cookie" = [])
+    )
+)]
+pub async fn set_default_branch(
+    service: web::Data<AppService>,
+    session: Session,
+    path: web::Path<PathParams>,
+) -> Result<HttpResponse, AppError> {
+    service
+        .repo
+        .repo_set_default_branch(&session, &path.workspace_name, &path.repo_name, path.branch_id)
+        .await?;
+
+    Ok(HttpResponse::Ok().json(ApiResponse::new("Default branch set successfully".to_string())))
+}