Add genlocke creation wizard with backend API and 4-step frontend

Implements the genlocke creation feature end-to-end: Genlocke and
GenlockeLeg models with migration, POST /genlockes endpoint that
creates the genlocke with all legs and auto-starts the first run,
and a 4-step wizard UI (Name, Select Games with preset templates,
Rules, Confirm) at /genlockes/new.

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

frontend/src/pages/index.ts

@@ -1,4 +1,5 @@
 export { Home } from './Home'
+export { NewGenlocke } from './NewGenlocke'
 export { NewRun } from './NewRun'
 export { RunList } from './RunList'
 export { RunEncounters } from './RunEncounters'