🛡️ Sentinel: [CRITICAL] Fix SQL injection vulnerability in db.py

[davidjuarezdev]

🚨 Severity: CRITICAL
💡 Vulnerability: SQL injection vulnerability in streamrip/db.py's contains and remove methods. The previous implementation validated dynamic **items dictionary keys using assert, which is stripped when Python is run with optimizations (e.g., python -O). In the remove method, keys weren't validated at all. This allowed arbitrary, malicious strings to be directly interpolated into the SQLite query strings (f"{key}=?").
🎯 Impact: An attacker could craft arbitrary **kwargs that bypass the identifier restrictions of standard python variable names, subsequently injecting malicious SQL fragments into dynamic query execution.
🔧 Fix: Replaced the fragile assert statements with explicit if key not in allowed_keys: raise ValueError(...) loops, applying this robust schema validation to both contains and remove methods prior to SQL construction.
✅ Verification: Formatting and linting checks run successfully (poetry run ruff check). The comprehensive test suite passes via poetry run pytest tests.

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PR created automatically by Jules for task 10316247338205181248 started by @davidjuarezdev