Improve spam detection with profile photo check & account age

[SaharPak]

Context

Current spam detection in spam_checker.py uses basic heuristics (username presence, name length, bio patterns). We can improve accuracy with more signals.

Requirements

• Use bot.get_user_profile_photos(user_id) to check if user has a profile photo
• Check account age if available (newer accounts = higher risk)
• Add configurable weight system for each signal
• Track false positive/negative rate in DB (Phase 1 DB issue dependency)

Signals to add

• No profile photo: +0.15 spam score
• Account created < 7 days ago: +0.25
• Username matches common spam patterns (e.g., user12345678): +0.2
• Name contains emojis/special chars excessively: +0.1

Acceptance Criteria

• Profile photo check integrated
• Spam scoring is configurable via config
• Unit tests for each signal