chore(server/membership): seed AI points for free and plus default plans

Free plan now ships with 10 AI points/month and Plus with 1000, replacing
the placeholder zeroes left over when the feature was first wired up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/configs/config.yaml

@@ -92,7 +92,7 @@ membership:
       name: Free
       article_generation: 3
       article_quota_cycle: lifetime
-      ai_points_monthly: 0
+      ai_points_monthly: 10
       ai_point_base_chars: 1000
       image_storage_bytes: 10485760
       company_limit: 1
@@ -102,7 +102,7 @@ membership:
       name: Plus
       article_generation: 200
       article_quota_cycle: monthly
-      ai_points_monthly: 0
+      ai_points_monthly: 1000
       ai_point_base_chars: 1000
       image_storage_bytes: 524288000
       company_limit: 1