Add boss battles, level caps, and badge tracking

Introduces full boss battle system: data models (BossBattle, BossPokemon,
BossResult), API endpoints for CRUD and per-run defeat tracking, and frontend
UI including a sticky level cap bar with badge display on the run page,
interleaved boss battle cards in the encounter list, and an admin panel
section for managing boss battles and their pokemon teams.

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

.beans/nuzlocke-tracker-gvom--boss-battles-level-caps-badges.md

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+---
+# nuzlocke-tracker-gvom
+title: Boss Battles, Level Caps & Badges
+status: completed
+type: feature
+priority: normal
+created_at: 2026-02-08T10:09:33Z
+updated_at: 2026-02-08T10:15:38Z
+---
+
+Add boss battle data models, API endpoints, and UI for gym leaders, elite four, champion, etc. Includes:
+- Backend models (BossBattle, BossPokemon, BossResult)
+- Database migration
+- API endpoints for CRUD and run tracking
+- Frontend types, API client, hooks
+- Sticky level cap bar on run page
+- Boss battle cards interleaved in encounter list
+- Admin panel for managing boss battles
+
+## Checklist
+
+- [x] Phase 1: Backend models & migration
+- [x] Phase 2: Backend schemas
+- [x] Phase 3: Backend API endpoints
+- [x] Phase 4: Frontend types, API & hooks
+- [x] Phase 5: Frontend run page (level cap bar + boss cards)
+- [x] Phase 6: Frontend admin panel