feat(admin): manually edit scene inputs (content elements)

Scene content elements (the editable Text/Media/Color/… inputs inside a scene)
had no CRUD — only AEP-import created them, so admins couldn't define or edit
them. Added full management:

content-svc:
- SceneElementsController: GET/POST/PUT/DELETE /v1/scene-elements?scene_id=
- SceneColorService: Get/Create/Update/DeleteContentElementAsync
- ContentElementResponse + SaveContentElementRequest (key, title, type,
  default_value, hint, position, text-box/font/media flags)
gateway: route /v1/scene-elements/*path → content
frontend: SceneColorEditor scenes tab → per-scene "ورودی‌ها" expander with full
  add/edit/delete of inputs (15 element types: Text/Media/Color/Number/…)

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

services/content/FlatRender.ContentSvc/Application/Services/SceneColorService.cs

@@ -174,6 +174,63 @@ public class SceneColorService(ContentDbContext db)
                 p.Items.OrderBy(i => i.Sort).Select(i => new ColorPresetItemResponse(i.Id, i.ElementKey, i.Value, i.Sort)).ToList()))
             .FirstAsync();
 
+    // ── Scene content elements (editable inputs) ────────────────────────────
+
+    public async Task<List<ContentElementResponse>> GetContentElementsAsync(Guid sceneId) =>
+        await db.SceneContentElements.Where(e => e.SceneId == sceneId)
+            .OrderBy(e => e.PositionInContainer)
+            .Select(e => ToElementResponse(e)).ToListAsync();
+
+    public async Task<ContentElementResponse> CreateContentElementAsync(SaveContentElementRequest req)
+    {
+        var e = new SceneContentElement { SceneId = req.SceneId };
+        ApplyElement(e, req);
+        db.SceneContentElements.Add(e);
+        await db.SaveChangesAsync();
+        return ToElementResponse(e);
+    }
+
+    public async Task<ContentElementResponse> UpdateContentElementAsync(Guid id, SaveContentElementRequest req)
+    {
+        var e = await db.SceneContentElements.FindAsync(id)
+            ?? throw new KeyNotFoundException($"Element {id} not found");
+        ApplyElement(e, req);
+        await db.SaveChangesAsync();
+        return ToElementResponse(e);
+    }
+
+    public async Task DeleteContentElementAsync(Guid id)
+    {
+        var e = await db.SceneContentElements.FindAsync(id)
+            ?? throw new KeyNotFoundException($"Element {id} not found");
+        db.SceneContentElements.Remove(e);
+        await db.SaveChangesAsync();
+    }
+
+    private static void ApplyElement(SceneContentElement e, SaveContentElementRequest req)
+    {
+        e.Key = req.Key;
+        e.Title = req.Title;
+        e.Hint = req.Hint;
+        e.Type = Enum.TryParse<ContentElementType>(req.Type, true, out var t) ? t : ContentElementType.Text;
+        e.DefaultValue = req.DefaultValue;
+        e.PositionInContainer = req.PositionInContainer;
+        e.IsTextBox = req.IsTextBox;
+        e.MaxSize = req.MaxSize;
+        e.FontSize = req.FontSize;
+        e.IsFontChangeable = req.IsFontChangeable;
+        e.IsFontSizeChangeable = req.IsFontSizeChangeable;
+        e.VideoSupport = req.VideoSupport;
+        e.Width = req.Width;
+        e.Height = req.Height;
+        e.Thumbnail = req.Thumbnail;
+    }
+
+    private static ContentElementResponse ToElementResponse(SceneContentElement e) => new(
+        e.Id, e.SceneId, e.Key, e.Title, e.Hint, e.Type.ToString(), e.DefaultValue,
+        e.PositionInContainer, e.IsTextBox, e.MaxSize, e.FontSize, e.IsFontChangeable,
+        e.IsFontSizeChangeable, e.VideoSupport, e.Width, e.Height, e.Thumbnail);
+
     // ── helpers ─────────────────────────────────────────────────────────────
 
     private static SceneResponse ToSceneResponse(Scene s) => new(

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

@@ -32,6 +32,33 @@ public class ScenesController(SceneColorService svc) : ControllerBase
     }
 }
 
+[ApiController]
+[Route("v1/scene-elements")]
+public class SceneElementsController(SceneColorService svc) : ControllerBase
+{
+    [HttpGet]
+    public async Task<IActionResult> List([FromQuery(Name = "scene_id")] Guid sceneId) =>
+        Ok(await svc.GetContentElementsAsync(sceneId));
+
+    [Authorize(Roles = "Admin")]
+    [HttpPost]
+    public async Task<IActionResult> Create([FromBody] SaveContentElementRequest req) =>
+        Ok(await svc.CreateContentElementAsync(req));
+
+    [Authorize(Roles = "Admin")]
+    [HttpPut("{id:guid}")]
+    public async Task<IActionResult> Update(Guid id, [FromBody] SaveContentElementRequest req) =>
+        Ok(await svc.UpdateContentElementAsync(id, req));
+
+    [Authorize(Roles = "Admin")]
+    [HttpDelete("{id:guid}")]
+    public async Task<IActionResult> Delete(Guid id)
+    {
+        await svc.DeleteContentElementAsync(id);
+        return NoContent();
+    }
+}
+
 [ApiController]
 [Route("v1/shared-colors")]
 public class SharedColorsController(SceneColorService svc) : ControllerBase

services/content/FlatRender.ContentSvc/Models/SceneColor.cs

@@ -48,3 +48,21 @@ public record ColorPresetItemInput(string ElementKey, string Value, int Sort);
 public record SaveColorPresetRequest(
     Guid ProjectId, string? Name, int Sort, List<ColorPresetItemInput> Items
 );
+
+// ── Scene content elements (the editable inputs inside a scene) ───────────────
+
+public record ContentElementResponse(
+    Guid Id, Guid SceneId, string Key, string Title, string? Hint,
+    string Type, string? DefaultValue, int PositionInContainer,
+    bool IsTextBox, int? MaxSize, int? FontSize, bool IsFontChangeable,
+    bool IsFontSizeChangeable, bool VideoSupport, int? Width, int? Height,
+    string? Thumbnail
+);
+
+public record SaveContentElementRequest(
+    Guid SceneId, string Key, string Title, string? Hint,
+    string Type, string? DefaultValue, int PositionInContainer,
+    bool IsTextBox, int? MaxSize, int? FontSize,
+    bool IsFontChangeable, bool IsFontSizeChangeable,
+    bool VideoSupport, int? Width, int? Height, string? Thumbnail
+);