refactor(B1): migrate to domain-driven project structure

Move all models/schemas/services/routers into app/domains/.
Keep backward-compat shims in old locations for imports.
Preserves domains/rendering/tasks.py from Phase A.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/domains/rendering/service.py

@@ -0,0 +1,14 @@
+"""Rendering services — template resolution, dispatch, and Blender utilities."""
+
+# Re-export from original service files for backward compatibility.
+from app.services.template_service import resolve_template, get_material_library_path
+from app.services.render_dispatcher import dispatch_render
+from app.services.render_blender import find_blender, is_blender_available
+
+__all__ = [
+    "resolve_template",
+    "get_material_library_path",
+    "dispatch_render",
+    "find_blender",
+    "is_blender_available",
+]