IAV-254/feat: Add Blocked Keywords Management with Automatic Normalization

Overview

Adds blocked keywords management for customer care agents with automatic normalization.

Features

• ✅ Automatic lowercase conversion
• ✅ Automatic duplicate removal
• ✅ Whitespace trimming
• ✅ Empty string filtering
• ✅ Clear all keywords with empty array []

Technical Details

• Validation: Keywords must be 1-100 characters
• Duplicates counted in input list
• Transaction management for updates

Closes IAV-254