Enhance packages API with pagination, filtering, and metadata

Backend changes:
- Add format and platform columns to Package model with validation
- Add database migrations for new columns with indexes
- Create PackageDetailResponse schema with aggregated fields:
  - tag_count, artifact_count, total_size
  - latest_tag, latest_upload_at
  - recent_tags (last 5 tags)
- Update list_packages endpoint:
  - Add pagination (page, limit)
  - Add search by name/description
  - Add sort (name, created_at, updated_at) and order (asc, desc)
  - Add format and platform filters
  - Return aggregated metadata for each package
- Add GET /api/v1/project/{project}/packages/{package_name} endpoint
  - Returns single package with full metadata
  - Optional include_tags parameter for all tags
- Update create_package to accept format and platform

Frontend changes:
- Update Package type with format, platform, and optional metadata fields
- Update listPackages to handle paginated response

frontend/src/api.ts

@@ -45,7 +45,8 @@ export async function getProject(name: string): Promise<Project> {
 // Package API
 export async function listPackages(projectName: string): Promise<Package[]> {
   const response = await fetch(`${API_BASE}/project/${projectName}/packages`);
-  return handleResponse<Package[]>(response);
+  const data = await handleResponse<PaginatedResponse<Package>>(response);
+  return data.items;
 }
 
 export async function createPackage(projectName: string, data: { name: string; description?: string }): Promise<Package> {