slskd: scaffold reverse-proxy sidecar

Add officer-slskd, a singleton sidecar that reverse-proxies to a
self-hosted slskd (Soulseek) instance and reports its loopback port to
the API on connect. All slskd knowledge (URL + API key) lives in the
sidecar; the platform is a thin auth+forward proxy for /api/slskd/* and
holds no slskd credentials. Mirrors the officer-vault pattern.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ecosystem.config.cjs

@@ -48,5 +48,11 @@ module.exports = {
       args: 'run src/servers/sidecar/vault/index.ts',
       watch: false,
     },
+    {
+      name: 'officer-slskd',
+      script: 'bun',
+      args: 'run src/servers/sidecar/slskd/index.ts',
+      watch: false,
+    },
   ],
 };