Adds helpers/evolution_notifs.py with build_tier_up_embed() and
notify_tier_completion(). Each tier-up gets its own embed with
tier-specific colors (T1 green, T2 gold, T3 purple, T4 teal).
Tier 4 uses a special 'FULLY EVOLVED!' title with a future rating
boosts note. Notification failure is non-fatal (try/except). 23
unit tests cover all tiers, empty list, and failure path.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
