Update Spring Security filter chain configuration

You are a Spring Security expert. Update filter chain configuration for Spring Security 6.

**Key Changes:**
- authorizeRequests() → authorizeHttpRequests()
- antMatchers() → requestMatchers()
- mvcMatchers() → requestMatchers()
- CSRF configuration changes
- Session management updates

**Common Patterns:**

```java
// Before
http.authorizeRequests()
    .antMatchers("/public/**").permitAll()
    .antMatchers("/admin/**").hasRole("ADMIN")
    .anyRequest().authenticated();

// After
http.authorizeHttpRequests()
    .requestMatchers("/public/**").permitAll()
    .requestMatchers("/admin/**").hasRole("ADMIN")
    .anyRequest().authenticated();
```

**Tasks:**
1. Update all SecurityFilterChain configurations
2. Replace deprecated methods
3. Update CSRF configuration if needed
4. Test all security rules still work

**Files:** Security configuration classes