fix: base64-encode Patchmon Basic auth credentials server-side

Patchmon's API uses standard RFC 7617 Basic auth — `Basic base64(token_key:token_secret)`. The handler was sending the api_token field verbatim, so it only worked if the user had manually base64-encoded the credential. After a Patchmon upgrade, the sync started returning HTML (the SPA, served when auth is rejected) and failing with "Unexpected token '<'" on JSON.parse.

Now: if the token contains ':' (raw key:secret), encode it server-side; otherwise pass through unchanged for backward compatibility. UI gets a placeholder hint showing the expected format.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/jobs.js

@@ -41,8 +41,14 @@ async function patchmonSyncHandler(cfg) {
   const { api_url, api_token } = cfg;
   if (!api_url || !api_token) throw new Error('Patchmon not configured — set API URL and token');
 
+  // Accept raw "key:secret" (recommended) or a pre-encoded base64 string.
+  // ":" cannot appear in a valid base64 string, so it's a reliable discriminator.
+  const credential = api_token.includes(':')
+    ? Buffer.from(api_token).toString('base64')
+    : api_token;
+
   const res = await fetch(api_url, {
-    headers: { Authorization: `Basic ${api_token}` },
+    headers: { Authorization: `Basic ${credential}` },
   });
   if (!res.ok) throw new Error(`Patchmon API ${res.status}`);