🛡️ Sentinel: [CRITICAL] Fix credential exposure in database setup command

[keough99]

🚨 Severity: CRITICAL
💡 Vulnerability: The levelerdb setup command in the leveler cog accepted plain-text MySQL credentials (including passwords) in public server channels, exposing these credentials in the channel's chat history.
🎯 Impact: Unauthorized users in the channel could view the bot owner's database credentials, leading to a complete compromise of the backend database.
🔧 Fix: Modified levelerdb_setup to explicitly check if ctx.guild: and enforce execution in Direct Messages. If accidentally run in a public channel, the command attempts to delete the user's message (await ctx.message.delete()) to prevent credential leakage and returns a warning.
✅ Verification: Tested syntax compilation of leveler/commands.py and ensured tests pass.

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PR created automatically by Jules for task 9186182412396689472 started by @keough99

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