feat(presets): admin preset stories (premade example videos) end-to-end

Epic A — admins author premade example videos per template; users pick one
on the template detail page to start a pre-filled project.

Backend (content-svc):
- PresetStory DTOs + PresetStoryService (admin CRUD + public published-only
  filter via role check + soft-delete) + PresetStoriesController (/v1/preset-stories)
- DI registration; gateway route /v1/preset-stories (optionalAuth, public read)

Frontend:
- ProjectPresetStories admin authoring UI (name/description/demo upload/published/
  sort + scene picker with order+duration + advanced scenes_spa); «ویدیوهای نمونه»
  button + modal in ProjectsAdmin
- TemplateDetailExamples renders real published stories (image/video preview,
  hover → "use this example" → creates a pre-bound project), falls back to
  placeholders when none; selected aspect's variant id keys the fetch
- public /api/preset-stories route; preset_story_id plumbed through
  createProjectFromTemplate + projects POST route; usePreset i18n (fa+en)

Verified: full CRUD via gateway (public hides unpublished); creating a project
with presetStoryId persists selected_preset_story_id on the saved project.

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

src/app/api/preset-stories/route.ts

@@ -0,0 +1,28 @@
+import { NextResponse } from "next/server";
+
+import { gatewayFetch } from "@/lib/api/gateway";
+
+export const dynamic = "force-dynamic";
+
+const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+/**
+ * Public list of PUBLISHED preset stories (premade example videos) for a content
+ * project. No auth → the gateway/content-svc returns published stories only, which
+ * is exactly what the template-detail "example videos" section needs.
+ */
+export async function GET(request: Request) {
+  const projectId = new URL(request.url).searchParams.get("project_id") ?? "";
+  if (!UUID_RE.test(projectId)) {
+    return NextResponse.json({ stories: [] });
+  }
+  try {
+    const res = await gatewayFetch(`/v1/preset-stories/?project_id=${projectId}`);
+    if (!res.ok) return NextResponse.json({ stories: [] });
+    const data = await res.json().catch(() => null);
+    const stories = Array.isArray(data) ? data : (data?.data ?? []);
+    return NextResponse.json({ stories });
+  } catch {
+    return NextResponse.json({ stories: [] });
+  }
+}

src/app/api/projects/route.ts

@@ -43,6 +43,8 @@ const createProjectSchema = z.object({
   // The original/template project id may be passed explicitly or carried inside
   // scene_data.templateId by the legacy create helpers.
   original_project_id: z.string().uuid().optional(),
+  // Start the project pre-bound to an admin-authored preset story (premade video).
+  preset_story_id: z.string().uuid().optional(),
 });
 
 export async function GET() {
@@ -109,6 +111,7 @@ export async function POST(request: Request) {
   const result = await createSavedProject({
     original_project_id: contentProjectId,
     name: parsed.data.name,
+    preset_story_id: parsed.data.preset_story_id,
     copy_default_values: true,
   });