Update the SecurityConfig

Added @EnableWebFluxSecurity and @EnableReactiveMethodSecurity. Injected the custom manager and converter. Disabled CSRF, HTTP Basic, Form Login. Set NoOpServerSecurityContextRepository for statelessness. Configured authorizeExchange rules. Added custom exception handling for 401/403 responses. Added the AuthenticationWebFilter correctly.

@Configuration
@EnableWebFluxSecurity // Enable Spring Security for WebFlux
@EnableReactiveMethodSecurity // Enable method-level security like @PreAuthorize
@EnableConfigurationProperties(JwtProperties::class) // Enable processing of JwtProperties