bug: legacy experiences added using script do not preserve their original age

[shub2726]

description

legacy experiences that were added using the backfill script all have their createdAt field set to 30 sept 2025, even though they were originally older entries.

because of this:

• when sorting experiences by recent, these legacy entries incorrectly appear before genuinely recent ones.
• in the future, if we add features like ai summaries or use createdat for sorting elsewhere, we will have to handle these legacy records separately, which complicates logic unnecessarily.

expected behavior

legacy experiences should have a createdAt value that reflects their approximate original timeline, not the script insertion date.

actual behavior

all legacy experiences added through the script show createdAt = 30 sept 2025.

steps to reproduce

1. view the list of experiences.
2. sort by recent.
3. notice that legacy experiences show up before newer ones.

suggested fix

write a one-time migration script to update these legacy records and assign them an arbitrary but consistent date (e.g., sometime in 2022) so that they no longer interfere with sorting or downstream features.