Add player profiles and community settings

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/migrations/016_community_settings_and_stats.sql

@@ -0,0 +1,20 @@
+-- +mixmaker Up
+CREATE TABLE community_settings (
+    singleton boolean PRIMARY KEY DEFAULT true CHECK (singleton),
+    discord_invite_url text NOT NULL DEFAULT '',
+    updated_at timestamptz NOT NULL DEFAULT now(),
+    updated_by text REFERENCES accounts(id)
+);
+
+INSERT INTO community_settings(singleton) VALUES (true)
+ON CONFLICT(singleton) DO NOTHING;
+
+CREATE INDEX IF NOT EXISTS series_event_id_idx
+    ON series ((body->>'eventId'));
+CREATE INDEX IF NOT EXISTS events_completed_starts_at_idx
+    ON events (starts_at DESC) WHERE state = 'Completed';
+
+-- +mixmaker Down
+DROP INDEX IF EXISTS events_completed_starts_at_idx;
+DROP INDEX IF EXISTS series_event_id_idx;
+DROP TABLE IF EXISTS community_settings;