perf(mcp): index server_id on LiteLLM_MCPUserEnvVars for orphan cleanup

The (user_id, server_id) unique index cannot serve the
delete_many(where={server_id}) orphan cleanup in delete_mcp_server,
since server_id is not the leading column, so it falls back to a full
table scan. Add a server_id index to cover that delete path

litellm-proxy-extras/litellm_proxy_extras/migrations/20260520120000_add_mcp_env_vars/migration.sql

@@ -18,3 +18,6 @@ CREATE UNIQUE INDEX IF NOT EXISTS "LiteLLM_MCPUserEnvVars_user_id_server_id_key"
 
 -- CreateIndex
 CREATE INDEX IF NOT EXISTS "LiteLLM_MCPUserEnvVars_user_id_idx" ON "LiteLLM_MCPUserEnvVars"("user_id");
+
+-- CreateIndex
+CREATE INDEX IF NOT EXISTS "LiteLLM_MCPUserEnvVars_server_id_idx" ON "LiteLLM_MCPUserEnvVars"("server_id");

litellm-proxy-extras/litellm_proxy_extras/schema.prisma

@@ -381,6 +381,7 @@ model LiteLLM_MCPUserEnvVars {
 
   @@unique([user_id, server_id])
   @@index([user_id])
+  @@index([server_id])
 }
 
 // Generate Tokens for Proxy

litellm/proxy/schema.prisma

@@ -381,6 +381,7 @@ model LiteLLM_MCPUserEnvVars {
 
   @@unique([user_id, server_id])
   @@index([user_id])
+  @@index([server_id])
 }
 
 // Generate Tokens for Proxy

schema.prisma

@@ -381,6 +381,7 @@ model LiteLLM_MCPUserEnvVars {
 
   @@unique([user_id, server_id])
   @@index([user_id])
+  @@index([server_id])
 }
 
 // Generate Tokens for Proxy