fix: trade-pro review fixes — drop shadow blocks.css, English presets, 7-item fallback nav

- remove themes/trade-pro/blocks.css (52-byte placeholder shadowed the
  platform 7KB block stylesheet via copy_blocks_css) and drop it from
  manifest styles; Phase 3 brings real component styles
- page-presets.json: all editor/bootstrap copy translated to trade B2B
  English; ids, block types, structure and hrefs identical to industrial
- fallback nav widened to all 7 default sections (Brands/Cases restored)
  so the documented false-positive window only relabels, never drops
  coverage; comment added next to the tp_needs_en_nav set
- test anchors '>Products<' on the built home page

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

tests/test_theme_registry.py

@@ -110,6 +110,7 @@ def test_trade_pro_builds_real_site(factory):
     home = factory.get(f'/preview/{sid}/{bid}/')
     assert home.status_code == 200, home.text[:400]
     assert 'lang="en"' in home.text
+    assert '>Products<' in home.text  # English fallback nav actually rendered
     assert '>首页<' not in home.text
     assert '<meta name="theme-color" content="#0b3d91"' in home.text