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>

.beans/nuzlocke-tracker-25mh--genlocke-tracking.md

@@ -73,11 +73,11 @@ A dedicated page showing:
 7. **Gauntlet/Retire HoF rule** — Enforce the "retire" mechanic with cumulative dupe list
 
 ## Success Criteria
-- [ ] A user can create a new genlocke via a multi-step wizard (name, game selection with presets, rules)
-- [ ] Games can be selected using True Genlocke, Normal Genlocke, or Custom presets, grouped by region
-- [ ] Nuzlocke rules are configured once and applied uniformly to all legs
-- [ ] Genlocke-specific rules (Keep HoF / Retire HoF) can be selected
-- [ ] The first leg starts automatically upon genlocke creation
+- [x] A user can create a new genlocke via a multi-step wizard (name, game selection with presets, rules)
+- [x] Games can be selected using True Genlocke, Normal Genlocke, or Custom presets, grouped by region
+- [x] Nuzlocke rules are configured once and applied uniformly to all legs
+- [x] Genlocke-specific rules (Keep HoF / Retire HoF) can be selected
+- [x] The first leg starts automatically upon genlocke creation
 - [ ] Each leg is a full nuzlocke run, tracked identically to standalone runs
 - [ ] Completing a leg triggers a transfer step where surviving Pokemon can be carried forward
 - [ ] Failing a leg marks the entire genlocke as failed