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Verified: full CRUD via gateway (public hides unpublished); creating a project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>

services/content/FlatRender.ContentSvc/Controllers/PresetStoriesController.cs

@@ -0,0 +1,43 @@
+using FlatRender.ContentSvc.Application.Services;
+using FlatRender.ContentSvc.Models;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace FlatRender.ContentSvc.Controllers;
+
+[ApiController]
+[Route("v1/preset-stories")]
+public class PresetStoriesController(PresetStoryService svc) : ControllerBase
+{
+    // Anonymous + non-admin callers only see published stories; admins see drafts too.
+    private bool IsAdmin => User.IsInRole("Admin");
+
+    [HttpGet]
+    public async Task<IActionResult> List([FromQuery(Name = "project_id")] Guid projectId) =>
+        Ok(await svc.GetByProjectAsync(projectId, publishedOnly: !IsAdmin));
+
+    [HttpGet("{id:guid}")]
+    public async Task<IActionResult> Get(Guid id)
+    {
+        var s = await svc.GetAsync(id, publishedOnly: !IsAdmin);
+        return s == null ? NotFound() : Ok(s);
+    }
+
+    [Authorize(Roles = "Admin")]
+    [HttpPost]
+    public async Task<IActionResult> Create([FromBody] SavePresetStoryRequest req) =>
+        Ok(await svc.CreateAsync(req));
+
+    [Authorize(Roles = "Admin")]
+    [HttpPut("{id:guid}")]
+    public async Task<IActionResult> Update(Guid id, [FromBody] SavePresetStoryRequest req) =>
+        Ok(await svc.UpdateAsync(id, req));
+
+    [Authorize(Roles = "Admin")]
+    [HttpDelete("{id:guid}")]
+    public async Task<IActionResult> Delete(Guid id)
+    {
+        await svc.DeleteAsync(id);
+        return NoContent();
+    }
+}