fix: Vultr relay 서버 API 구조 변경 적용

- Base URL: /v2 경로 추가
- 인증 헤더: X-API-Key → Authorization: Bearer
- relay 서버가 Vultr API와 동일한 구조로 변경됨

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

src/connectors/vultr.ts

@@ -81,7 +81,8 @@ export class VultrConnector {
     env?: Env
   ) {
     // Use relay server by default, allow override via parameter or environment variable
-    this.baseUrl = relayUrl || 'https://vultr-relay.anvil.it.com';
+    // Relay server mirrors Vultr API structure: /v2/regions, /v2/plans
+    this.baseUrl = relayUrl || 'https://vultr-relay.anvil.it.com/v2';
 
     // Rate limit: 3000 requests/hour = ~0.83 requests/second
     // Use 0.8 to be conservative
@@ -296,7 +297,7 @@ export class VultrConnector {
       const response = await fetch(url, {
         method: 'GET',
         headers: {
-          'X-API-Key': this.apiKey,
+          'Authorization': `Bearer ${this.apiKey}`,
           'Content-Type': 'application/json',
           'Accept': 'application/json',
           'User-Agent': 'Mozilla/5.0 (compatible; CloudInstancesAPI/1.0)',