perf(db): optimize SQL history pruning to use batching instead of per-insert COUNT(*)

[ZhuchkaTriplesix]

Closes #525

Summary of Changes

• Introduced _historyInsertCounts in LocalDb to track insertions per history bucket.
• Updated recordSqlQueryHistory to trigger _pruneSqlQueryHistoryBucket lazily in batches of 10 insertions (reducing SQLite COUNT(*) and DELETE overhead by 90% during query execution).
• Retained instant pruning for small caps (maxEntries <= 10) and explicit forcePrune: true for full backward compatibility with existing tests.
• Added unit tests for batched history pruning in test/core/storage/sql_query_history_test.dart.

Verification

• flutter test test/core/storage/sql_query_history_test.dart passed (8/8 tests).