fix: add pg_trgm extension to database schema

Adds pg_trgm extension to enable GIN indexes for fuzzy text
search functionality. This extension provides trigram matching
required by word_similarity() function used in unified search.

Resolves container startup failures when GIN indexes with gin_trgm_ops
are created without the extension being loaded.

database/schema/schema.sql

@@ -1,6 +1,9 @@
 -- Consolidated Bookhoard Database Schema
 -- This file contains the complete current schema for the Bookhoard media library management system
 
+-- Create extensions for full-text search and fuzzy matching
+CREATE EXTENSION IF NOT EXISTS pg_trgm;
+
 -- Create library types table
 CREATE TABLE IF NOT EXISTS library_types (
     id UUID PRIMARY KEY DEFAULT gen_random_uuid(),