Add SearchReindexJob to repopulate the search index (#2850)

Rebuilds search records for every published Card and every Comment on a
published Card. Intended for manual invocation after a search-index loss
event — not a recurring job.

Uses ActiveJob::Continuable so the work survives worker restarts and
resumes from the last-processed id. The job is idempotent.

Removes script/maintenance/reindex_stale_search_records.rb, which was
written against a different hypothesis (a date-cutoff backfill) and is
superseded by this unconditional repair job.

script/maintenance/reindex_stale_search_records.rb

@@ -1,39 +0,0 @@
-# Reindex cards and comments that may be missing from the search index.
-#
-# The data import path (Account::DataTransfer) uses insert_all! which bypasses
-# ActiveRecord callbacks, so imported cards and comments never get search records
-# created. This script reindexes cards and comments created before a cutoff date.
-#
-# Usage:
-#   bin/rails runner script/maintenance/reindex_stale_search_records.rb              # default cutoff: 2025-11-13
-#   bin/rails runner script/maintenance/reindex_stale_search_records.rb 2026-01-01   # custom cutoff
-
-cutoff = Date.parse(ARGV[0] || "2025-11-13")
-
-puts "Reindexing cards and comments created before #{cutoff}..."
-
-cards = Card.published.where("created_at < ?", cutoff).includes(:rich_text_description)
-card_count = cards.count
-puts "Found #{card_count} cards to reindex"
-
-reindexed_cards = 0
-cards.find_each do |card|
-  card.reindex
-  reindexed_cards += 1
-  print "\rCards: #{reindexed_cards}/#{card_count}" if reindexed_cards % 100 == 0
-end
-puts "\rCards: #{reindexed_cards}/#{card_count}"
-
-comments = Comment.joins(:card).merge(Card.published).where("comments.created_at < ?", cutoff).includes(:rich_text_body, :card)
-comment_count = comments.count
-puts "Found #{comment_count} comments to reindex"
-
-reindexed_comments = 0
-comments.find_each do |comment|
-  comment.reindex
-  reindexed_comments += 1
-  print "\rComments: #{reindexed_comments}/#{comment_count}" if reindexed_comments % 100 == 0
-end
-puts "\rComments: #{reindexed_comments}/#{comment_count}"
-
-puts "Done! Reindexed #{reindexed_cards} cards and #{reindexed_comments} comments."