Fix History tab crash: coerce Ivanti note fields to strings before rendering

PostgreSQL + Ivanti API enrichment can return non-string values
(objects/arrays) for currentStateUserNotes and similar fields.
React crashes silently (blank page, no console error) when trying
to render non-string values as children. Same root cause pattern
as Bug 3 in ivanti-panel-bugs-2026-05-12.

Added safeText() wrapper that coerces any non-string truthy value
to a JSON string before rendering in the History tab notes section.

Also fixed flaky property test: fc.date() could generate invalid
dates causing RangeError on .toISOString(). Added .filter() guard
and explicit UTC date bounds.

backend/__tests__/fp-submissions-cleanup.property.test.js

@@ -31,7 +31,9 @@ const lifecycleStatusArb = fc.constantFrom('submitted', 'approved', 'rejected',
 
 const dismissedAtArb = fc.oneof(
     fc.constant(null),
-    fc.date({ min: new Date('2020-01-01'), max: new Date('2030-12-31') }).map(d => d.toISOString())
+    fc.date({ min: new Date('2020-01-01T00:00:00.000Z'), max: new Date('2030-12-31T00:00:00.000Z') })
+        .filter(d => !isNaN(d.getTime()))
+        .map(d => d.toISOString())
 );
 
 const submissionArb = fc.record({