fix: JAR upload — increase multipart limit and fix storage permissions

Spring Boot defaults to 1MB max file size which rejected all JAR
uploads. Set to 200MB to match the configured max-jar-size. Also
create /data/jars with cameleer user ownership in the Dockerfile
so the non-root process can write uploaded JARs.

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

src/main/resources/application.yml

@@ -5,6 +5,10 @@ server:
 spring:
   application:
     name: cameleer-saas
+  servlet:
+    multipart:
+      max-file-size: 200MB
+      max-request-size: 200MB
   datasource:
     url: ${SPRING_DATASOURCE_URL:jdbc:postgresql://postgres:5432/cameleer_saas}
     username: ${SPRING_DATASOURCE_USERNAME:cameleer}