feat(database): Engine-level Write-Ahead Logging & concurrency buffers for SQLite (#477)

[ayushshukla1807]

Systems Execute: SQLite High-Concurrency Engine (#477)

The Attack Vector:

Issue #477 identifies critical SQLite Database is Locked race conditions specifically targeting the montage-beta staging environment, preventing reliable CI tests or concurrent admin evaluations natively.

The Architecture:

While application logic (like DAO mappings) runs asynchronously across Clastic loops,
the underlying SQLite Engine historically boots in DELETE journal mode, which structurally blocks multi-threaded write pipelines.

This Pull Request physically intercepts the SQLAlchemy connection builder loop and natively inserts a strict SQLite Engine PRAGMA override protocol:

• Write-Ahead Logging (journal_mode=WAL): Instigated immediately upon create_engine, allowing simultaneous, non-blocking readers and writers without crashing the application interface natively.
• Thread Saturation Timers (busy_timeout=5000): Safely caches internal block conflicts up to 5 seconds automatically to let race sequences clear natively before explicitly dropping a sequence cleanly.
• Environment Safety Hooks: Explicitly constrained exclusively within SQL Dialect discriminators (sqlite in db_url), securely preventing MySQL mutations natively when running on Toolforge!