feat(render+admin): stop a render job (admin, any owner)

The render-queue cancel button used the owner-scoped /cancel (WHERE user_id=…),
so an admin couldn't stop another user's job. Added:
- render-svc: POST /v1/renders/:job_id/stop (admin-gated) → store.StopJob cancels
  any in-progress job regardless of owner and frees the assigned node
- admin: render-queue button now "توقف" → /api/admin/renders/{id}/stop (with confirm)

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

services/render/internal/handlers/renders.go

@@ -131,6 +131,21 @@ func (h *RenderHandler) Cancel(c *gin.Context) {
 	})
 }
 
+// POST /v1/renders/:job_id/stop — admin: stop any user's in-progress job
+func (h *RenderHandler) Stop(c *gin.Context) {
+	jobID, err := uuid.Parse(c.Param("job_id"))
+	if err != nil {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid job_id"})
+		return
+	}
+	stopped, err := h.store.StopJob(c.Request.Context(), jobID)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"stopped": stopped})
+}
+
 // POST /v1/renders/:job_id/retry
 func (h *RenderHandler) Retry(c *gin.Context) {
 	userID := middleware.GetUserID(c)