Scaffold cameleer3-server project structure

Multi-module Maven project (server-core + server-app) with Spring Boot 3.4.3,
Gitea CI workflow, and dependency on cameleer3-common from Gitea Maven registry.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

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+# Maven
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+.mvn/timing.properties
+.mvn/wrapper/maven-wrapper.jar
+
+# IDE
+.idea/
+*.iml
+.project
+.classpath
+.settings/
+.factorypath
+*.swp
+*.swo
+*~
+.vscode/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Build artifacts
+*.jar
+!.mvn/wrapper/*.jar
+*.war
+*.ear
+*.class
+
+# Logs
+*.log
+logs/
+
+# Claude
+.claude/