Add pokemon status management with death tracking

Implement status change workflow (alive → dead) with confirmation modal,
death cause recording, and visual status indicators on pokemon cards.
Includes backend migration for death_cause field and graveyard view
on the run dashboard.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/types/game.ts

@@ -48,6 +48,7 @@ export interface Encounter {
   status: EncounterStatus
   catchLevel: number | null
   faintLevel: number | null
+  deathCause: string | null
   caughtAt: string
 }
 
@@ -97,6 +98,7 @@ export interface UpdateEncounterInput {
   nickname?: string
   status?: EncounterStatus
   faintLevel?: number
+  deathCause?: string
 }
 
 // Re-export for convenience