fix(stats): fall back to Default deck when deck config is blank

- Trim deck name before checking falsy so empty string uses Default
- Add fake AnkiConnect server helper and regression test for blank deck

src/core/services/stats-server.ts

@@ -1101,7 +1101,7 @@ export function createStatsApp(
     }
 
     const model = ankiConfig.isLapis?.sentenceCardModel || 'Basic';
-    const deck = ankiConfig.deck ?? 'Default';
+    const deck = ankiConfig.deck?.trim() || 'Default';
     const tags = ankiConfig.tags ?? ['SubMiner'];
 
     try {