feat(gui): sidebar sections + non-technical tool labels

Sidebar nav now groups tools under Data Review / Data Cleaners /
Transformations / Automations via st.navigation, replacing the flat
auto-discovered list. Tool display names switch to action-first
phrasing (Find Duplicates, Fix Missing Values, Find Unusual Values,
Standardize Formats, Clean Text, Quality Check, Map Columns, Combine
Files, Automated Workflows) in EN + ES packs and on each page's H1.

The Data Cleaners section follows the requested order: Missing
Values → Outliers → Text Cleaner → Format Standardizer → Deduplicator
→ Quality Check. (Text Cleaner kept inside cleaners since the request
didn't list it but the tool still ships.) Registry now carries a
section field; helpers added: tools_in_section(), section_label().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/gui/test_gate.py

@@ -45,7 +45,7 @@ class TestGateNoUpload:
         text = collected_text(app)
         # The dedup page title is the unambiguous signal that the gate
         # didn't short-circuit.
-        assert "Deduplicator" in text
+        assert "Find Duplicates" in text
 
     def test_no_upload_no_gate_warning(self, app_factory):
         app = app_factory(GATED_PAGE)