feat(FN-4042): add SQLite lock contention recovery in core database layer

Adds SQLite lock contention recovery for WAL-mode databases, covering both the core database layer (db.ts, central-db.ts, store.ts) and the run-audit subsystem, with comprehensive unit and integration test coverage and updated storage documentation.

Fusion-Task-Id: FN-4042

.changeset/fn-4042-sqlite-lock-recovery.md

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+---
+"@runfusion/fusion": patch
+---
+
+Improve SQLite write reliability under transient multi-connection lock contention by adding bounded recovery for outer write transactions, keeping task mutations and run-audit inserts atomic during executor-driven writes.