chore: Set backend.embedded to true for all-in-one packaging

The embedded flag must be true for the portable exe to work.
When embedded is false, the app expects an external backend.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/config.json

@@ -8,7 +8,7 @@
     "compute": "int8"
   },
   "backend": {
-    "embedded": false,
+    "embedded": true,
     "host": "127.0.0.1",
     "port": 8000,
     "database": {