feat(agents): add Prisma migration for agent header columns

ALTER TABLE LiteLLM_AgentsTable to add:
- static_headers JSONB DEFAULT '{}'
- extra_headers TEXT[] DEFAULT ARRAY[]::TEXT[]

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

litellm-proxy-extras/litellm_proxy_extras/migrations/20260305000000_add_agent_headers/migration.sql

@@ -0,0 +1,5 @@
+-- Add static_headers and extra_headers to LiteLLM_AgentsTable
+
+ALTER TABLE "LiteLLM_AgentsTable"
+  ADD COLUMN IF NOT EXISTS "static_headers" JSONB DEFAULT '{}',
+  ADD COLUMN IF NOT EXISTS "extra_headers"  TEXT[] DEFAULT ARRAY[]::TEXT[];