feat(federation): update key path handling and ensure directory creation for federation keys

compose.yml

@@ -7,6 +7,7 @@ services:
     env_file: ".env"
     volumes:
       - uploads:/app/uploads
+      - ./keys:/app/keys
     depends_on:
       postgres:
         condition: service_healthy

server/config/federation.js

@@ -13,7 +13,11 @@ let publicKeyPem = '';
 
 // Load or generate Ed25519 keys
 if (FEDERATION_DOMAIN) {
-    const keyPath = path.join(__dirname, 'federation_key.pem');
+    const keyPath = process.env.FEDERATION_KEY_PATH || '/app/keys/federation_key.pem';
+    const keyDir = path.dirname(keyPath);
+    if (!fs.existsSync(keyDir)) {
+        fs.mkdirSync(keyDir, { recursive: true });
+    }
 
     if (!privateKeyPem && fs.existsSync(keyPath)) {
         privateKeyPem = fs.readFileSync(keyPath, 'utf8');