Add RDP debug logging and enable guacd debug level

- docker-compose: override guacd command with -L debug flag so FreeRDP
  errors are visible in `docker logs mremotify-guacd-1`
- rdp.ts: log RDP host/user, arg names, ready instruction, proxy-mode
  entry, and any error/disconnect instructions from guacd

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

backend/src/websocket/rdp.ts

@@ -128,6 +128,8 @@ export async function rdpWebsocket(fastify: FastifyInstance) {
         return;
       }
 
+      fastify.log.info({ host: conn.host, port: conn.port, user: conn.username }, 'RDP: starting guacd handshake');
+
       try {
         // 1. Select protocol
         guacd.write(buildInstruction('select', conn.protocol));
@@ -135,6 +137,7 @@ export async function rdpWebsocket(fastify: FastifyInstance) {
         // 2. Read args list from guacd
         const argsInstruction = await readInstruction(guacd, tcpBuf);
         const argNames = argsInstruction.slice(1);
+        fastify.log.info({ argNames }, 'RDP: guacd args list received');
 
         const decryptedPassword = conn.encryptedPassword ? decrypt(conn.encryptedPassword) : '';
 
@@ -162,6 +165,7 @@ export async function rdpWebsocket(fastify: FastifyInstance) {
 
         // 4. Read ready instruction
         const readyInstruction = await readInstruction(guacd, tcpBuf);
+        fastify.log.info({ readyInstruction }, 'RDP: guacd ready instruction received');
         if (readyInstruction[0] !== 'ready') {
           throw new Error(`guacd handshake failed: expected 'ready', got '${readyInstruction[0]}'`);
         }
@@ -185,12 +189,22 @@ export async function rdpWebsocket(fastify: FastifyInstance) {
         return;
       }
 
+      fastify.log.info({ uuid: readyInstruction[1] }, 'RDP: entering proxy mode');
+
       // --- Proxy mode ---
       guacd.on('data', (data: Buffer) => {
-        if (socket.readyState === WebSocket.OPEN) socket.send(data.toString('utf8'));
+        const text = data.toString('utf8');
+        // Log the first message from guacd (usually an error or first instruction)
+        if (text.startsWith('5.error') || text.startsWith('10.disconnect')) {
+          fastify.log.warn({ guacdMsg: text.substring(0, 200) }, 'RDP: guacd sent error/disconnect');
+        }
+        if (socket.readyState === WebSocket.OPEN) socket.send(text);
       });
 
-      guacd.on('end', () => socket.close());
+      guacd.on('end', () => {
+        fastify.log.info('RDP: guacd TCP connection ended');
+        socket.close();
+      });
       guacd.on('error', (err) => {
         fastify.log.warn({ err }, 'guacd socket error');
         socket.close(1011, err.message);