feat: Add Pre-Execution Warning for High-Cardinality Queries in Production

[krasnovdm]

Problem
Users can accidentally execute high-cardinality queries (e.g., FullScan/TableLookUp on large tables) directly in production databases via the UI, causing performance degradation or outages.

Proposed Solution
Implement a pre-execution safety check:

1. Run EXPLAIN to estimate query cardinality and resource impact
2. If high-risk conditions are detected and target is production DB:
   • Show prominent modal warning with text:

   "This query may severely impact database performance. I understand the risks and wish to proceed."

   • Require explicit user confirmation (checkbox + button)
3. Criteria for triggering:
   • Full table scans on large datasets
   • Missing shard keys in filters
   • High estimated row processing