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/i18n/packs/en.json

@@ -99,40 +99,51 @@
   },
   "tools": {
     "01_deduplicator": {
-      "name": "Deduplicator",
+      "name": "Find Duplicates",
       "description": "Fuzzy matching, normalization, survivor selection, and interactive review."
     },
     "02_text_cleaner": {
-      "name": "Text Cleaner",
+      "name": "Clean Text",
       "description": "Whitespace trim, multi-space collapse, Unicode normalization, BOM and line-ending handling."
     },
     "03_format_standardizer": {
-      "name": "Format Standardizer",
+      "name": "Standardize Formats",
       "description": "Standardize dates, currencies, names, phone numbers, and addresses."
     },
     "04_missing_handler": {
-      "name": "Missing Value Handler",
+      "name": "Fix Missing Values",
       "description": "Detect disguised nulls, missingness analysis, and imputation strategies."
     },
     "05_column_mapper": {
-      "name": "Column Mapper",
+      "name": "Map Columns",
       "description": "Rename columns, enforce a target schema, and coerce types."
     },
     "06_outlier_detector": {
-      "name": "Outlier Detector",
+      "name": "Find Unusual Values",
       "description": "Z-score, IQR, and MAD detection with domain-rule violations and winsorization."
     },
     "07_multi_file_merger": {
-      "name": "Multi-File Merger",
+      "name": "Combine Files",
       "description": "Combine multiple CSV/Excel files with schema alignment."
     },
     "08_validator_reporter": {
-      "name": "Validator & Reporter",
+      "name": "Quality Check",
       "description": "Validate against rules and generate PDF/Excel quality reports."
     },
     "09_pipeline_runner": {
-      "name": "Pipeline Runner",
+      "name": "Automated Workflows",
       "description": "Chain tools in recommended order and pass output between steps."
     }
+  },
+  "nav": {
+    "section_review": "Data Review",
+    "section_cleaners": "Data Cleaners",
+    "section_transformations": "Transformations",
+    "section_automations": "Automations",
+    "review_page_title": "Review",
+    "home_page_title": "Home",
+    "section_account": "Account",
+    "activate_title": "Activate",
+    "close_title": "Close"
   }
 }