In older app versions simpleSettings was stored as a directory. Reading
it as a file threw EISDIR which was caught/logged but saveSimpleStore()
would subsequently fail with an uncaught EISDIR when writing to the
same path.
- Catch EISDIR in loadSimpleStoreAll and rename legacy dir to .bak
- Catch EISDIR in saveSimpleStore, remove dir and retry write
- Replace module-level DATA_PATH with lazy getDataPath() to fix
stale path when --user-data-dir or Snap overrides userData
- Remove debug console.log that leaked settings to stdout
- Replace console.error with electron-log for consistency
Closes#4791
