Fix: enable WAL and batch writes in TelemetryStore to avoid SQLITE_BUSY under concurrency

[selena731]

Enable WAL mode and batch commits in TelemetryStore to prevent SQLITE_BUSY and reduce I/O.

Changes:

• Set PRAGMA journal_mode=WAL and PRAGMA synchronous=NORMAL when opening TelemetryStore connection
• Replace per-insert commit() with buffered/batched commits (e.g., commit every N inserts or time-based flush)
• Add unit tests to simulate concurrent writes and verify no SQLITE_BUSY raised
• Add migration notes if needed

[SoulSniper-V2]

take