Delete blog sx_components.py — move all rendering to callers

Move remaining 19 rendering functions from the 2487-line
sx_components.py to their direct callers:

- menu_items/routes.py: menu item form, page search, nav OOB
- post/admin/routes.py: calendar view, associated entries, nav OOB
- sxc/pages/__init__.py: editor panel, post data inspector, preview,
  entries browser, settings form, edit page editor
- bp/blog/routes.py: inline new post page composition

Move load_service_components() call from sx_components module-level
to setup_blog_pages() so .sx files still load at startup.

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

blog/app.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 import path_setup  # noqa: F401  # adds shared/ to sys.path
-import sx.sx_components as sx_components  # noqa: F401  # ensure Hypercorn --reload watches this file
 from pathlib import Path
 
 from quart import g, request