Add unit tests for spam_checker.py heuristics

[SaharPak]

Context

The spam detection logic in src/services/spam_checker.py has no tests yet. This is a great first contribution — no Telegram API knowledge needed.

What to do

1. Create tests/test_spam_checker.py
2. Write tests for the heuristic scoring (not the AI parts):
   • User with no username → score increases
   • User with short name → score increases
   • Bot user → high score
   • Normal user → approved
   • Message with spam patterns → detected
   • Clean message → passes

Tips

• Mock the AI functions (they call external APIs)
• Use pytest and pytest-asyncio
• Run with: pytest tests/

Acceptance Criteria

• At least 8 test cases covering main paths
• Tests pass with pytest
• No external API calls in tests (mock AI)

[yoelchemla]

Hi, I would like to work on this issue.
Is it still available?

[SaharPak]

@yoelchemla yes, please go ahead