refactor: use crustdata enrichment source only for new member profiles (CM-924)

[skwowet]

What changed

• Crustdata now runs only once per member. In isEnrichableBySource, we check if a Crustdata cache row already exists for the member (regardless of whether data is null or not). If it does, the member has already been through Crustdata and we skip it.
• Preserved existing cache data on re-enrichment. In enrichMember, when a source returns null but the cache already holds valid data, we now refresh the cache timestamp instead of overwriting with null. This prevents Crustdata data from being wiped when its cache becomes obsolete after 90 days and the source intentionally skips the member.

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Note

Medium Risk
Changes enrichment eligibility and cache update behavior, which can affect which sources run and whether cached profiles are retained; risk is moderated by being localized to the enrichment worker and primarily gatekeeping/DB-write logic.

Overview
Crustdata enrichment is now one-shot per member: isEnrichableBySource loads cache rows even when data is null and skips Crustdata entirely if any Crustdata cache row already exists for that member.

The enrichment workflow now avoids wiping valid cached data: when a source returns null but the cache has non-null data, it only updates cache.updatedAt instead of overwriting the cache with null (supporting sources that intentionally skip members).

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[cursor]

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