Add regression tests for the popularity/EV score

Ports tests/test_popularity_score.py from the Lotto sibling project
(same purpose: pin down known overplayed combinations scoring lower
than spread ones), adapted for 5 main numbers and adds coverage for
the Euro-number determinism bug fixed in 0285a1c (tips #1-3 used to
always return the identical pair). Also documents beautifulsoup4 as
a required dependency in the README, which was missing despite
update_from_eurojackpot_zahlen_eu.py needing it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -57,7 +57,7 @@ Eurojackpot/
 ```bash
 python3 -m venv venv
 source venv/bin/activate
-pip install pandas numpy scikit-learn requests torch
+pip install pandas numpy scikit-learn requests torch beautifulsoup4
 ```
 
 ### 2. Telegram-Bot einrichten
@@ -139,6 +139,15 @@ Tipp, Ø Confidence/Quality, Trefferauswertung).
 Alle Generierungen werden in `data/generated_tips/generation_history.json`
 protokolliert, alle Ziehungsauswertungen in `data/learning_log.json`.
 
+## 🧪 Tests
+
+Regressionstests für den Popularity/EV-Score (`tests/test_popularity_score.py`):
+
+```bash
+pip install pytest
+pytest tests/
+```
+
 ## 🗂️ Datenformat
 
 `data/AlleEurojackpotzahlen.csv` (Semikolon-getrennt):