Replace RCON with API-only emulator transport

- Switch default EMULATOR_MODE from 'rcon' to 'api'
- Remove RCON_HOST/PORT/timeout/maxRetries env vars
- Add EMULATOR_API_URL to .env and .env.example
- Update createEmulatorTransport() to use HTTP API only
- Remove rconHost/port from offline alert context
- All 827 tests pass, TypeScript compiles cleanly

src/lib/services/alert.ts

@@ -223,10 +223,8 @@ export function emulatorOffline(detail?: string): Promise<SendAlertResult> {
 		severity: "critical",
 		message: detail
 			? `Emulator appears offline: ${detail}`
-			: "Emulator appears offline — RCON connection could not be established.",
+			: "Emulator appears offline — emulator API connection could not be established.",
 		context: {
-			rconHost: env.RCON_HOST,
-			rconPort: env.RCON_PORT,
 			...(detail ? { detail } : {}),
 		},
 	});