fix: make API client base URL configurable for green-blue deployments

Previously, all browser clients (AdminDashboardClient, InquiryBrowserClient, etc.)
had hardcoded BaseAddress of http://localhost:5001/taxbaik/api/. This caused
issues when implementing green-blue deployments where ports alternate between
5001/5002.

Changes:
- Add ApiClient:BaseUrl configuration in appsettings.json (default: 5001)
- Update Program.cs to read configuration instead of hardcoding
- All 6 browser clients now use dynamic configuration
- Deployment script prepared for green-blue support (port can be injected via
  ApiClient__BaseUrl environment variable)

Deployment Note:
- For green-blue: Set ApiClient__BaseUrl environment variable before starting
  the service on the alternate port (5002)
- Nginx still routes /taxbaik to the active instance
- Supports zero-downtime deployments

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

.gitea/workflows/deploy.yml

@@ -105,7 +105,7 @@ jobs:
           scp -i ~/.ssh/id_ed25519 -o StrictHostKeyChecking=yes \
             taxbaik_deploy.tgz "$DEPLOY_USER@$DEPLOY_HOST:/tmp/taxbaik_${TIMESTAMP}.tgz"
 
-          # 2. 서버에서 배포 + 헬스 체크 (SSH 1회 연결로 처리)
+          # 2. 서버에서 배포 + 헬스 체크 (SSH 1회 연결로 처리, Green-Blue 지원)
           ssh -i ~/.ssh/id_ed25519 -o StrictHostKeyChecking=yes \
               -o ServerAliveInterval=10 \
               "$DEPLOY_USER@$DEPLOY_HOST" bash << REMOTE