Fix hashtags not being picked up when full-width hash sign is used (#36103)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/models/tag.rb

@@ -41,7 +41,7 @@ class Tag < ApplicationRecord
   HASHTAG_LAST_SEQUENCE = '([[:word:]_]*[[:alpha:]][[:word:]_]*)'
   HASHTAG_NAME_PAT = "#{HASHTAG_FIRST_SEQUENCE}|#{HASHTAG_LAST_SEQUENCE}".freeze
 
-  HASHTAG_RE = %r{(?<![=/)\p{Alnum}])#(#{HASHTAG_NAME_PAT})}
+  HASHTAG_RE = %r{(?<![=/)\p{Alnum}])[#|＃](#{HASHTAG_NAME_PAT})}
   HASHTAG_NAME_RE = /\A(#{HASHTAG_NAME_PAT})\z/i
   HASHTAG_INVALID_CHARS_RE = /[^[:alnum:]\u0E47-\u0E4E#{HASHTAG_SEPARATORS}]/