fix: revert to public/ brand assets — DS exports field blocks imports

The @cameleer/design-system package.json exports field doesn't include
assets/, causing production build failures. Copy PNGs to public/ and
reference via basePath until DS adds asset exports.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/SecurityConfig.java

@@ -95,6 +95,7 @@ public class SecurityConfig {
                                 "/index.html",
                                 "/config.js",
                                 "/favicon-*.png",
+                                "/cameleer3-logo-*.png",
                                 "/assets/**"
                         ).permitAll()