Enhance overview metrics and data density

[BM-Haoh]

Updates the Overview embed to serve as a comprehensive dashboard, consolidating performance data and recent history into a single view.

Technical Requirements:

• Stats Integration: Maintain current avarage stats from the last tournament.
• Match history: Maintain current last 5 matches with opponent and result.
• Map context (New): Add a section for Map-related info
  • Current priority: Global Attack/Defense win rates and overall Win % per map in the current pool

Notes:

• This layout serves as a bridge until the head-to-head command is implemented. Once that command is live, map-specific compositions and deep-dives will be migrated there to keep the Overview "lean".

Tasks:

• Update brain.py logic to calculate global Atk/Def win rates (already have it for each map, so it will be a small task)
• Refactor the Overview embed construction in info-time