feat(security): add password complexity validator

- Implement strict password requirements:
  - Minimum 8 characters
  - At least one uppercase letter
  - At least one lowercase letter
  - At least one number
  - At least one special character
- Add custom validator for Echo integration
- Add GetPasswordRequirements helper function
- Add ValidatePassword function for manual validation

database/schema/schema.sql

@@ -32,6 +32,16 @@ CREATE TABLE users (
     updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
 );
 
+-- Create refresh_tokens table
+CREATE TABLE refresh_tokens (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    token VARCHAR(255) UNIQUE NOT NULL,
+    expires_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    revoked_at TIMESTAMP WITH TIME ZONE
+);
+
 -- Create libraries table
 CREATE TABLE libraries (
     id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
@@ -189,6 +199,8 @@ WHERE lt.name = 'ebooks';
 CREATE INDEX idx_users_email ON users(email);
 CREATE INDEX idx_users_username ON users(username);
 CREATE INDEX idx_library_types_name ON library_types(name);
+CREATE INDEX idx_refresh_tokens_token ON refresh_tokens(token);
+CREATE INDEX idx_refresh_tokens_user_id ON refresh_tokens(user_id);
 
 -- Library indexes
 CREATE INDEX idx_libraries_name ON libraries(name);