[BUG] Cannot List Oracle DB Schemas

## Description
Cannot list schemas within Oracle DB, which then lists the tables.

## Steps to Reproduce
Connect to a OracleDB, see "No structures found".

## Expected Behavior
Lst schemas within Oracle DB, which then lists the tables.

## Actual Behavior
Upon connecting I see "No structures found".

## Environment
Please provide the following information:

- **LibreDB Studio Version**: 0.15.0
- **Browser**: Chrome
- **OS**: macOS
- **Node.js/Bun Version**: Why are you asking me? It's your Docker image...
- **Database Type**: Oracle DB Enterprise
- **Database Version**: Unknown

## Possible Solution
Actually test these database connections instead of just vibe coding.