🛡️ Sentinel: [CRITICAL] Fix DuckDB SQL injection vulnerability in adapter

[aperetti]

🚨 Severity: CRITICAL
💡 Vulnerability: SQL Injection in DuckDB via f-string query construction in backend/src/shared/meter_adapters/duckdb_adapter.py. User-supplied timestamp inputs were directly interpolated into SQL commands (e.g., f"... WHERE r.timestamp >= '{st_lit}'::TIMESTAMP").
🎯 Impact: Exploitation could allow arbitrary execution of DuckDB queries, leading to data exposure, modification, or potentially system disruption within the local DuckDB session context.
🔧 Fix:

1. Replaced f-string interpolation with DuckDB's parameterized query placeholders (?::TIMESTAMP).
2. Updated all conn.execute and EXPLAIN ANALYZE calls to explicitly pass parameter lists [start_time, end_time].
3. Updated the test_duckdb_adapter.py test suite to assert the presence of parameterized placeholders and correctly formatted parameters.

✅ Verification:

1. Ran the backend tests suite successfully using cd backend && PYTHONPATH=. PARQUET_DIR=../data python3 -m pytest tests/test_duckdb_adapter.py.
2. Verified all tests passed ensuring regressions were not introduced.

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PR created automatically by Jules for task 8668451605904462662 started by @aperetti

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