feat(tournaments): add partnership tracking and tournament management

Implement comprehensive partnership tracking system and tournament
management features including round-robin, single/double elimination,
and Swiss system pairings.

Changes:
- Add partnership_games and partnership_stats tables
- Implement PartnershipTracker service for recording partnership data
- Add tournament generator with multiple formats
- Create tournament management actions and views
- Add acceptance tests for partnership tracking
- Fix PartnershipTracker to use single snapshot per player per match
- Fix round-robin test to query by round_number instead of hardcoded ID

Note: All 8 acceptance tests now passing

db/migrate/20240915000004_create_event_participants.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+ROM::SQL.migration do
+  change do
+    create_table :event_participants do
+      primary_key :id
+      foreign_key :event_id, :events, null: false
+      foreign_key :player_id, :players, null: false
+      foreign_key :team_id, :teams
+      column :status, String, default: 'registered'  # registered, checked_in, active, eliminated
+      column :seed, Integer
+      column :registration_date, DateTime, null: false, default: Sequel::CURRENT_TIMESTAMP
+    end
+
+    add_index :event_participants, [:event_id, :player_id], unique: true
+    add_index :event_participants, [:event_id, :team_id]
+  end
+end