feat(render B2): render binder writes user edits into AE before render

Edits previously never reached the MP4 (the node rendered template defaults). Now:
- render-svc claim includes the saved input values as bindings (GetRenderBindings →
  saved_scene_contents with non-empty value).
- node-agent: new binder.go emits a JSON bind-spec + downloads media locally, runs the
  pre-existing data-driven bind.jsx via afterfx (sets text layers' Source Text, replaces
  media footage), saves a bound.aep next to the template, then aerender renders THAT.
- 12-min timeout + fresh-AE + done-marker polling (mirrors scan). Non-fatal: on bind
  failure the job still renders template defaults.

Verified binding data flows (edited frl_c1t1/frl_c1t2 → claim bindings). Live MP4
verification needs the updated node-agent.exe re-run.

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

services/render/internal/handlers/internal.go

@@ -292,6 +292,10 @@ func (h *InternalHandler) Claim(c *gin.Context) {
 	// Composition to render (-comp). Non-fatal: empty → node uses the render queue.
 	compName, _ := h.store.GetTemplateCompName(c.Request.Context(), job.OriginalProjectID)
 
+	// User's edited input values → the node writes them into the AE project before
+	// rendering (render binder). Non-fatal: empty → renders template defaults.
+	bindings, _ := h.store.GetRenderBindings(c.Request.Context(), job.SavedProjectID)
+
 	c.JSON(http.StatusOK, models.ClaimedJob{
 		JobID:          job.ID,
 		SavedProjectID: job.SavedProjectID,
@@ -304,6 +308,7 @@ func (h *InternalHandler) Claim(c *gin.Context) {
 		IsBundle:       isBundle,
 		BundleMD5:      bundleMD5,
 		CompName:       compName,
+		Bindings:       bindings,
 	})
 }