Add API key authentication for proxy endpoints.

Support multiple API keys from config, env, and CLI, enforce auth on non-public endpoints, and pass keys through remote deploy verification.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

config.example.json

@@ -22,6 +22,10 @@
   "pipe": "",
   "websocket_url": "",
   "remote_auth_file": "/secrets/credentials.json",
+  "api_keys": [
+    "replace-with-long-random-key-1",
+    "replace-with-long-random-key-2"
+  ],
   "lingma_bootstrap_enabled": true,
   "lingma_source_type": "marketplace",
   "lingma_vsix_url": "",