* fix: Preserve transaction tags during rule application
When rules set tags, they now ADD to existing tags instead of replacing
them. This fixes issue #518 where tags were being removed during bank sync.
The root cause was that SetTransactionTags called enrich_attribute with
just the single tag from the rule, which replaced all existing tags.
Now it merges the new tag with existing tags using .uniq to prevent
duplicates.
This preserves:
- User-applied tags that shouldn't be overwritten by rules
- Tags from other rules when multiple rules match the same transaction
- Tags set during previous syncs
* fix: Add nil guard for tag in SetTransactionTags
Return early with 0 if the tag is not found, preventing NoMethodError
when find_by_id returns nil. This matches the pattern used in
SetTransactionMerchant.
---------
Co-authored-by: Claude <noreply@anthropic.com>
88241cf5cb