fix: Token-Abfrage in executeUnifiedPromptStream

Frontend:
- api.js Zeile 487: localStorage.getItem('token') → getToken()
- Token heißt 'bodytrack_token', nicht 'token'
- SSE-Requests bekamen undefined token → 401 Unauthorized

Root Cause:
- Admin verwendet executeUnifiedPrompt (normaler Request mit Header-Auth)
- Analyse verwendet executeUnifiedPromptStream (SSE mit Token im URL)
- SSE bekam keinen Token wegen falschem localStorage key

Fixes:
- "Connection to server lost" in Analyse-Seite

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/utils/api.js

@@ -484,7 +484,7 @@ export const api = {
 
     // TODO: Security improvement - use session cookie instead of token in URL
     // For now, send token as query param since EventSource doesn't support custom headers
-    const token = localStorage.getItem('token')
+    const token = getToken()
     if (token) params.append('token', token)
 
     if (modules) {