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>

src/gui/pages/5_Column_Mapper.py

@@ -39,7 +39,7 @@ require_normalization_gate()
 # Header
 # ---------------------------------------------------------------------------
 
-st.title("🗂️ Column Mapper")
+st.title("🗂️ Map Columns")
 st.caption(
     "Rename columns, enforce a target schema, and coerce types. Runs locally — "
     "your data never leaves this computer."