fix: Preserve tags on bulk edits (take 3) (#889)

* fix: handle tags separately from entryable_attributes in bulk updates

Tags use a join table (taggings) rather than a direct column, which means
empty tag_ids clears all tags rather than meaning "no change". This caused
bulk category-only edits to accidentally clear existing tags.

This fix:
- Removes tag_ids from entryable_attributes in Entry.bulk_update!
- Adds update_tags parameter to explicitly control tag updates
- Uses params.key?(:tag_ids) in controller to detect explicit tag changes
- Preserves existing tags when tag_ids is not provided in the request

This is a cleaner architectural solution compared to tracking "touched"
state in the frontend, as it properly acknowledges the semantic difference
between column attributes and join table associations.

https://claude.ai/code/session_014CsmTwjteP4qJs6YZqCKnY

* fix: handle tags separately in API transaction updates

Apply the same pattern to the API endpoint: tags are now handled
separately from entryable_attributes to distinguish between "not
provided" (preserve existing tags) and "explicitly set to empty"
(clear all tags).

This allows API consumers to:
- Update other fields without affecting tags (omit tag_ids)
- Clear all tags (send tag_ids: [])
- Set specific tags (send tag_ids: [id1, id2])

https://claude.ai/code/session_014CsmTwjteP4qJs6YZqCKnY

* Proposed fix

* fix: improve tag handling in bulk updates for transactions

* fix: allow bulk edit to clear/preserve tags by omitting hidden multi-select field

* PR comments

* Dumb copy/paste error

* Linter

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <jjmata@jjmata.com>

app/controllers/transactions/bulk_updates_controller.rb

@@ -6,7 +6,7 @@ class Transactions::BulkUpdatesController < ApplicationController
     updated = Current.family
                      .entries
                      .where(id: bulk_update_params[:entry_ids])
-                     .bulk_update!(bulk_update_params)
+                     .bulk_update!(bulk_update_params, update_tags: tags_provided?)
 
     redirect_back_or_to transactions_path, notice: "#{updated} transactions updated"
   end
@@ -16,4 +16,11 @@ class Transactions::BulkUpdatesController < ApplicationController
       params.require(:bulk_update)
             .permit(:date, :notes, :category_id, :merchant_id, entry_ids: [], tag_ids: [])
     end
+
+    # Check if tag_ids was explicitly provided in the request.
+    # This distinguishes between "user wants to update tags" vs "user didn't touch tags field".
+    def tags_provided?
+      bulk_update = params[:bulk_update]
+      bulk_update.respond_to?(:key?) && bulk_update.key?(:tag_ids)
+    end
 end