refactor: rebrand from net.siegeln to io.cameleer

Institutionalize the product identity ahead of public release:

- Java package: net.siegeln.cameleer.saas → io.cameleer.saas (109 files)
- Maven groupId: net.siegeln.cameleer → io.cameleer
- Public image defaults: gitea.siegeln.net/cameleer/ → registry.cameleer.io/cameleer/
- Updated docs (architecture, user-manual, HOWTO, runtime-loader README)
- Updated CLAUDE.md path references

Internal build infra (CI workflows, .gitmodules, npm registry, Maven repo)
intentionally kept at gitea.siegeln.net — code stays on internal Gitea.

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

pom.xml

@@ -11,7 +11,7 @@
         <relativePath/>
     </parent>
 
-    <groupId>net.siegeln.cameleer</groupId>
+    <groupId>io.cameleer</groupId>
     <artifactId>cameleer-saas</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>Cameleer SaaS Platform</name>