feat(Explorer): Enhance metric extraction, source transparency, and UI display

- **Standardization & Formula Logic:** Fixed NameError/SyntaxError in formula parser; added support for comments and capitalized placeholders.
- **Source URL Tracking:** Extended DB schema and cascade logic to store and track specific source URLs.
- **Frontend & UI:**
  - Added 'Standardized Potential' display in Inspector.
  - Added clickable source link with icon.
  - Fixed Settings tab layout collapse (flex-shrink-0).
- **Export Capabilities:**
  - Single-company JSON export now includes full quantitative metadata.
  - New global CSV export endpoint /api/companies/export.
- **System Integrity:**
  - Fixed Notion sync typo ('Stanardization').
  - Corrected Nginx proxy routing and FastAPI route ordering.
  - Ensured DB persistence via explicit docker-compose volume mapping.

company-explorer/backend/scripts/migrate_db.py

@@ -60,7 +60,8 @@ def migrate_tables():
             "calculated_metric_unit": "TEXT",
             "standardized_metric_value": "FLOAT",
             "standardized_metric_unit": "TEXT",
-            "metric_source": "TEXT"
+            "metric_source": "TEXT",
+            "metric_source_url": "TEXT"
         }
 
         for col, col_type in comp_migrations.items():