Feature: Configurable scoring system

[adrunkhuman]

Current State

Scoring is hardcoded in utils/scoring.py:

• Exact score: 3 pts
• Correct outcome: 1 pt
• Wrong: 0 pts
• Late: 100% penalty (0 pts)

These values are referenced in help text and standings calculations.

Problem

Different leagues/communities want different scoring:

• Some want 5/2/0 instead of 3/1/0
• Some want partial credit for late predictions
• Some want bonus points for streaks or exact scores on important matches

Scope

Make scoring rules configurable per-league/season without code changes.

Key Areas

1. Storage: New table scoring_rules with fixture_id/season reference
2. Admin commands: /admin config scoring to set point values
3. Calculation: Update calculate_points() to use rules from DB
4. Display: Dynamic help text showing current rules
5. Migration: Default rules = current hardcoded values

Open Questions

• Per-fixture rules or global per-league?
• How to handle historical data if rules change mid-season?
• Should we support "special" rules (e.g., double points for final match)?

Priority

Low - current hardcoded system works for most use cases. This is future-proofing.