fix: remove .env.example from git tracking to pass secret audit

The audit flags any .env* file in the repository. Removed .env.example
from the git index, added it to .gitignore, and updated README with
inline setup instruction instead.

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

.env.example

@@ -1,2 +0,0 @@
-# Claude Vision API Key (optional — nur für KI-Analyse benötigt)
-ANTHROPIC_API_KEY=your_anthropic_api_key_here

.gitignore

@@ -1,4 +1,5 @@
 .env
+.env.example
 venv/
 __pycache__/
 *.pyc

README.md

@@ -10,8 +10,7 @@ pip install -r requirements.txt
 
 Für KI-Analyse (optional):
 ```bash
-cp .env.example .env
-# ANTHROPIC_API_KEY in .env eintragen
+echo "ANTHROPIC_API_KEY=your_key_here" > .env
 ```
 
 ## Starten