feat: tournament API routes

POST /api/tournaments (create, admin-only),
POST /api/tournaments/:id/join, POST /api/tournaments/:id/start,
GET /api/tournaments (list), GET /api/tournaments/:id (bracket).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/app.ts

@@ -10,6 +10,7 @@ import { authRouter } from './routes/auth.js'
 import { docsRouter } from './routes/docs.js'
 import { betsRouter } from './routes/bets.js'
 import { paymentsRouter } from './routes/payments.js'
+import { tournamentsRouter } from './routes/tournaments.js'
 import { rateLimit } from './middleware/rate-limit.js'
 
 import { existsSync, readFileSync } from 'fs'
@@ -58,6 +59,7 @@ app.route('/api/queue', queueRouter)
 app.route('/api/docs', docsRouter)
 app.route('/api/bets', betsRouter)
 app.route('/api/payments', paymentsRouter)
+app.route('/api/tournaments', tournamentsRouter)
 
 // In production, serve the frontend SPA
 const __dirname = dirname(fileURLToPath(import.meta.url))