V1.5.0: Version bump + Download-Button Redesign

- Version auf 1.5.0 in allen Packages, CI, Dockerfile, Electron
- Download-Button im gleichen Design wie Version-Badge (bg-secondary, radius, hover accent)
- CI Registry auf adriahub (192.168.1.100:9080) umgestellt

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

electron/preload.js

@@ -2,5 +2,5 @@ const { contextBridge } = require('electron');
 
 contextBridge.exposeInMainWorld('electronAPI', {
   isElectron: true,
-  version: '1.0.0',
+  version: '1.5.0',
 });