docs: add NODE_MODULE_VERSION mismatch to troubleshooting guide

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

Author: sjsyrek

docs/TROUBLESHOOTING.md

@@ -372,6 +372,16 @@ rm ~/.cache/deepl-cli/cache.db   # or ~/.deepl-cli/cache.db for legacy installat
 deepl cache enable
 ```
 
+### "Cache database corrupted" with NODE_MODULE_VERSION mismatch
+
+**Cause:** The `better-sqlite3` native addon was compiled for a different Node.js version than the one currently running. This happens when you switch Node.js versions (e.g., via `nvm use`, `fnm`, or a system upgrade) without rebuilding native modules.
+
+**Solution:**
+
+```bash
+npm rebuild better-sqlite3
+```
+
 ---
 
 ## Document Translation Issues