feat(fullstack): Add JWT validation

legalconsenthub-backend/src/main/kotlin/com/betriebsratkanzlei/legalconsenthub/config/SecurityConfig.kt

@@ -0,0 +1,39 @@
+package com.betriebsratkanzlei.legalconsenthub.config
+
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import org.springframework.security.config.annotation.web.builders.HttpSecurity
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity
+import org.springframework.security.config.annotation.web.invoke
+import org.springframework.security.oauth2.jose.jws.SignatureAlgorithm
+import org.springframework.security.oauth2.jwt.JwtDecoder
+import org.springframework.security.oauth2.jwt.NimbusJwtDecoder
+import org.springframework.security.web.SecurityFilterChain
+
+@Configuration
+@EnableWebSecurity
+class SecurityConfig {
+
+    @Bean
+    fun securityFilterChain(http: HttpSecurity): SecurityFilterChain {
+        http {
+            csrf { disable() }
+            authorizeHttpRequests {
+                authorize("/swagger-ui/**", permitAll)
+                authorize("/v3/**", permitAll)
+                authorize(anyRequest, authenticated)
+            }
+            oauth2ResourceServer {
+                jwt { }
+            }
+        }
+
+        return http.build()
+    }
+
+    @Bean
+    fun jwtDecoder(): JwtDecoder {
+        return NimbusJwtDecoder.withJwkSetUri("http://192.168.178.105:3001/api/auth/jwks")
+            .jwsAlgorithm(SignatureAlgorithm.ES512).build()
+    }
+}