Fix slug conflict and seed import for Docker deployment

- Rename [id] → [competitionId] under /admin/competitions/ to fix
  Next.js "different slug names for same dynamic path" error
- Update params.id → params.competitionId in competition detail page
- Fix seed import: use .js extension for tsx ESM module resolution

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

prisma/seed.ts

@@ -18,7 +18,7 @@ import {
   AdvancementRuleType,
 } from '@prisma/client'
 import bcrypt from 'bcryptjs'
-import { defaultRoundConfig } from '../src/types/competition-configs'
+import { defaultRoundConfig } from '../src/types/competition-configs.js'
 import { readFileSync } from 'fs'
 import { parse } from 'csv-parse/sync'
 import { join, dirname } from 'path'