feat(admin): standalone Projects page + per-project asset manager

- content-svc: GET /v1/projects (browse/search all projects across containers,
  paginated, admin) returning template name/slug + AE status; project_assets
  table (mig 23) + entity; GET/POST/DELETE /v1/projects/{id}/assets
- /admin/projects: searchable, paginated list of every renderable project with
  thumbnail, template, aspect/resolution, AE-file + publish status
- ProjectAssets component: list/upload/delete named footage/image/audio/font
  files per project (reused in the projects page; AE file upload alongside)
- nav + fa/en "Projects" label

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/content/FlatRender.ContentSvc/Domain/Entities/ProjectAsset.cs

@@ -0,0 +1,15 @@
+namespace FlatRender.ContentSvc.Domain.Entities;
+
+/// <summary>A named asset file (footage/image/audio/font) attached to a project, alongside its .aep.</summary>
+public class ProjectAsset
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    public Guid ProjectId { get; set; }
+    public string Name { get; set; } = default!;
+    public string Kind { get; set; } = "footage"; // footage | image | audio | font | other
+    public string Url { get; set; } = default!;
+    public string? MinioKey { get; set; }
+    public long? SizeBytes { get; set; }
+    public int Sort { get; set; }
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+}